Add custom word entry + language pair support for learning units

- New UnitBuilder component with language pair selector (DE⇄EN, ES, FR, etc.)
- Manual word entry form with auto-suggest from Kaikki dictionary (6M words)
- "No results" prompt to add multi-word terms (e.g. "schottisches Hochland")
- New backend endpoint GET /vocabulary/lookup-translation (any→any via EN hub)
- Updated POST /vocabulary/units: accepts custom_words + source_lang/target_lang
- Split unit endpoints into vocabulary/unit_api.py (500 LOC budget)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

studio-v2/app/vocabulary/components/UnitBuilder.tsx

@@ -0,0 +1,307 @@
+'use client'
+
+import React, { useState, useCallback, useRef, useEffect } from 'react'
+
+/** Supported language pairs */
+const LANGUAGES = [
+  { code: 'en', label: 'Englisch' },
+  { code: 'de', label: 'Deutsch' },
+  { code: 'fr', label: 'Franzoesisch' },
+  { code: 'es', label: 'Spanisch' },
+  { code: 'it', label: 'Italienisch' },
+  { code: 'pt', label: 'Portugiesisch' },
+  { code: 'nl', label: 'Niederlaendisch' },
+  { code: 'tr', label: 'Tuerkisch' },
+  { code: 'ru', label: 'Russisch' },
+  { code: 'ar', label: 'Arabisch' },
+  { code: 'uk', label: 'Ukrainisch' },
+  { code: 'pl', label: 'Polnisch' },
+  { code: 'sv', label: 'Schwedisch' },
+  { code: 'da', label: 'Daenisch' },
+  { code: 'fi', label: 'Finnisch' },
+  { code: 'el', label: 'Griechisch' },
+  { code: 'hu', label: 'Ungarisch' },
+  { code: 'cs', label: 'Tschechisch' },
+  { code: 'ro', label: 'Rumaenisch' },
+]
+
+export interface UnitWord {
+  id: string
+  source_text: string
+  target_text: string
+  pos?: string
+  is_custom?: boolean
+}
+
+interface Props {
+  isDark: boolean
+  glassCard: string
+  glassInput: string
+  selectedWords: UnitWord[]
+  onWordsChange: (words: UnitWord[]) => void
+  onCreateUnit: (title: string, sourceLang: string, targetLang: string) => void
+  isCreating: boolean
+  noSearchResults?: boolean
+  searchQuery?: string
+}
+
+export default function UnitBuilder({
+  isDark, glassCard, glassInput,
+  selectedWords, onWordsChange, onCreateUnit, isCreating,
+  noSearchResults, searchQuery,
+}: Props) {
+  const [unitTitle, setUnitTitle] = useState('')
+  const [sourceLang, setSourceLang] = useState('de')
+  const [targetLang, setTargetLang] = useState('en')
+  const [showManualEntry, setShowManualEntry] = useState(false)
+  const [manualSource, setManualSource] = useState('')
+  const [manualTarget, setManualTarget] = useState('')
+  const [suggestions, setSuggestions] = useState<{ source_text: string; target_text: string; pos?: string }[]>([])
+  const [isLookingUp, setIsLookingUp] = useState(false)
+  const debounceRef = useRef<ReturnType<typeof setTimeout>>()
+
+  // Auto-suggest translation when typing in source field
+  useEffect(() => {
+    if (!manualSource.trim() || manualSource.length < 2) {
+      setSuggestions([])
+      return
+    }
+    if (debounceRef.current) clearTimeout(debounceRef.current)
+    debounceRef.current = setTimeout(async () => {
+      setIsLookingUp(true)
+      try {
+        const resp = await fetch(
+          `/api/vocabulary/lookup-translation?word=${encodeURIComponent(manualSource)}&source=${sourceLang}&target=${targetLang}&limit=5`
+        )
+        if (resp.ok) {
+          const data = await resp.json()
+          setSuggestions(data.results || [])
+          // Auto-fill target if exactly one match
+          if (data.results?.length === 1 && !manualTarget) {
+            setManualTarget(data.results[0].target_text)
+          }
+        }
+      } catch { /* ignore */ }
+      setIsLookingUp(false)
+    }, 400)
+    return () => { if (debounceRef.current) clearTimeout(debounceRef.current) }
+  }, [manualSource, sourceLang, targetLang]) // eslint-disable-line react-hooks/exhaustive-deps
+
+  const addManualWord = useCallback(() => {
+    if (!manualSource.trim() || !manualTarget.trim()) return
+    const newWord: UnitWord = {
+      id: `custom_${Date.now()}_${Math.random().toString(36).slice(2, 6)}`,
+      source_text: manualSource.trim(),
+      target_text: manualTarget.trim(),
+      is_custom: true,
+    }
+    onWordsChange([...selectedWords, newWord])
+    setManualSource('')
+    setManualTarget('')
+    setSuggestions([])
+  }, [manualSource, manualTarget, selectedWords, onWordsChange])
+
+  const removeWord = useCallback((id: string) => {
+    onWordsChange(selectedWords.filter(w => w.id !== id))
+  }, [selectedWords, onWordsChange])
+
+  const swapLanguages = useCallback(() => {
+    setSourceLang(targetLang)
+    setTargetLang(sourceLang)
+  }, [sourceLang, targetLang])
+
+  const srcLabel = LANGUAGES.find(l => l.code === sourceLang)?.label || sourceLang.toUpperCase()
+  const tgtLabel = LANGUAGES.find(l => l.code === targetLang)?.label || targetLang.toUpperCase()
+
+  return (
+    <div className="w-80 flex-shrink-0">
+      <div className={`${glassCard} rounded-2xl p-5 sticky top-6`}>
+        <h3 className={`text-lg font-semibold mb-3 ${isDark ? 'text-white' : 'text-slate-900'}`}>
+          Lernunit erstellen
+        </h3>
+
+        {/* Language pair selector */}
+        <div className="flex items-center gap-2 mb-3">
+          <select
+            value={sourceLang}
+            onChange={e => setSourceLang(e.target.value)}
+            className={`flex-1 px-2 py-1.5 rounded-lg border text-xs ${glassInput}`}
+          >
+            {LANGUAGES.map(l => (
+              <option key={l.code} value={l.code}>{l.label}</option>
+            ))}
+          </select>
+          <button
+            onClick={swapLanguages}
+            className={`px-2 py-1.5 rounded-lg text-sm ${isDark ? 'bg-white/10 text-white/60 hover:bg-white/20' : 'bg-slate-100 text-slate-500 hover:bg-slate-200'}`}
+            title="Sprachen tauschen"
+          >
+            ⇄
+          </button>
+          <select
+            value={targetLang}
+            onChange={e => setTargetLang(e.target.value)}
+            className={`flex-1 px-2 py-1.5 rounded-lg border text-xs ${glassInput}`}
+          >
+            {LANGUAGES.map(l => (
+              <option key={l.code} value={l.code}>{l.label}</option>
+            ))}
+          </select>
+        </div>
+
+        <input
+          type="text"
+          value={unitTitle}
+          onChange={e => setUnitTitle(e.target.value)}
+          placeholder="Titel (z.B. Unit 3 - Food)"
+          className={`w-full px-4 py-2.5 rounded-xl border outline-none text-sm mb-3 ${glassInput}`}
+        />
+
+        {/* Manual word entry toggle */}
+        <button
+          onClick={() => setShowManualEntry(!showManualEntry)}
+          className={`w-full text-xs px-3 py-2 rounded-lg mb-3 flex items-center justify-center gap-1 ${
+            showManualEntry
+              ? isDark ? 'bg-blue-500/20 text-blue-300' : 'bg-blue-100 text-blue-700'
+              : isDark ? 'bg-white/10 text-white/60 hover:bg-white/15' : 'bg-slate-100 text-slate-600 hover:bg-slate-200'
+          }`}
+        >
+          {showManualEntry ? '▾ Eigene Woerter eingeben' : '▸ Eigene Woerter eingeben'}
+        </button>
+
+        {/* Manual entry form */}
+        {showManualEntry && (
+          <div className={`rounded-xl p-3 mb-3 ${isDark ? 'bg-white/5' : 'bg-slate-50'}`}>
+            <div className="space-y-2">
+              <div>
+                <label className={`text-xs ${isDark ? 'text-white/50' : 'text-slate-500'}`}>
+                  {srcLabel}
+                </label>
+                <input
+                  type="text"
+                  value={manualSource}
+                  onChange={e => setManualSource(e.target.value)}
+                  placeholder={`z.B. ${sourceLang === 'de' ? 'schottisches Hochland' : 'Scottish Highlands'}`}
+                  className={`w-full px-3 py-2 rounded-lg border outline-none text-sm ${glassInput}`}
+                  onKeyDown={e => e.key === 'Enter' && manualTarget && addManualWord()}
+                />
+              </div>
+              <div>
+                <label className={`text-xs ${isDark ? 'text-white/50' : 'text-slate-500'}`}>
+                  {tgtLabel} {isLookingUp && <span className="animate-pulse">...</span>}
+                </label>
+                <input
+                  type="text"
+                  value={manualTarget}
+                  onChange={e => setManualTarget(e.target.value)}
+                  placeholder={`z.B. ${targetLang === 'en' ? 'Scottish Highlands' : 'schottisches Hochland'}`}
+                  className={`w-full px-3 py-2 rounded-lg border outline-none text-sm ${glassInput}`}
+                  onKeyDown={e => e.key === 'Enter' && manualSource && addManualWord()}
+                />
+              </div>
+              {/* Auto-suggest results */}
+              {suggestions.length > 1 && (
+                <div className={`rounded-lg p-2 space-y-1 ${isDark ? 'bg-white/5' : 'bg-white'}`}>
+                  <span className={`text-xs ${isDark ? 'text-white/40' : 'text-slate-400'}`}>Vorschlaege:</span>
+                  {suggestions.map((s, i) => (
+                    <button
+                      key={i}
+                      onClick={() => {
+                        setManualSource(s.source_text)
+                        setManualTarget(s.target_text)
+                      }}
+                      className={`w-full text-left text-xs px-2 py-1 rounded ${isDark ? 'hover:bg-white/10 text-white/70' : 'hover:bg-slate-100 text-slate-700'}`}
+                    >
+                      {s.source_text} → {s.target_text} {s.pos && <span className={isDark ? 'text-white/30' : 'text-slate-400'}>({s.pos})</span>}
+                    </button>
+                  ))}
+                </div>
+              )}
+              <button
+                onClick={addManualWord}
+                disabled={!manualSource.trim() || !manualTarget.trim()}
+                className={`w-full py-2 rounded-lg text-sm font-medium ${
+                  manualSource.trim() && manualTarget.trim()
+                    ? isDark ? 'bg-green-500/20 text-green-300 hover:bg-green-500/30' : 'bg-green-100 text-green-700 hover:bg-green-200'
+                    : isDark ? 'bg-white/5 text-white/20' : 'bg-slate-100 text-slate-300'
+                }`}
+              >
+                + Hinzufuegen
+              </button>
+            </div>
+          </div>
+        )}
+
+        {/* "No results" prompt to add manually */}
+        {noSearchResults && searchQuery && !showManualEntry && (
+          <div className={`rounded-xl p-3 mb-3 text-center ${isDark ? 'bg-amber-500/10 border border-amber-500/20' : 'bg-amber-50 border border-amber-200'}`}>
+            <p className={`text-xs mb-2 ${isDark ? 'text-amber-300' : 'text-amber-700'}`}>
+              &quot;{searchQuery}&quot; nicht im Woerterbuch
+            </p>
+            <button
+              onClick={() => {
+                setShowManualEntry(true)
+                setManualSource(searchQuery)
+              }}
+              className={`text-xs px-3 py-1.5 rounded-lg font-medium ${isDark ? 'bg-amber-500/20 text-amber-200 hover:bg-amber-500/30' : 'bg-amber-100 text-amber-800 hover:bg-amber-200'}`}
+            >
+              Manuell hinzufuegen →
+            </button>
+          </div>
+        )}
+
+        {/* Word list */}
+        {selectedWords.length === 0 ? (
+          <p className={`text-sm text-center py-6 ${isDark ? 'text-white/40' : 'text-slate-400'}`}>
+            Woerter aus dem Woerterbuch auswaehlen oder eigene eingeben
+          </p>
+        ) : (
+          <div className="space-y-1.5 max-h-72 overflow-y-auto mb-3">
+            {selectedWords.map((w, i) => (
+              <div key={w.id} className={`flex items-center justify-between px-3 py-2 rounded-lg ${isDark ? 'bg-white/5' : 'bg-slate-50'}`}>
+                <div className="flex items-center gap-2 min-w-0 flex-1">
+                  <span className={`text-xs w-5 text-center flex-shrink-0 ${isDark ? 'text-white/30' : 'text-slate-400'}`}>{i+1}</span>
+                  <div className="min-w-0 flex-1">
+                    <span className={`text-sm font-medium truncate block ${isDark ? 'text-white' : 'text-slate-900'}`}>
+                      {w.source_text}
+                    </span>
+                    <span className={`text-xs truncate block ${isDark ? 'text-white/40' : 'text-slate-400'}`}>
+                      {w.target_text}
+                    </span>
+                  </div>
+                  {w.is_custom && (
+                    <span className={`text-xs px-1.5 py-0.5 rounded flex-shrink-0 ${isDark ? 'bg-green-500/20 text-green-400' : 'bg-green-100 text-green-600'}`}>
+                      eigen
+                    </span>
+                  )}
+                </div>
+                <button
+                  onClick={() => removeWord(w.id)}
+                  className={`text-xs ml-2 flex-shrink-0 ${isDark ? 'text-red-400 hover:text-red-300' : 'text-red-500 hover:text-red-700'}`}
+                >
+                  ✕
+                </button>
+              </div>
+            ))}
+          </div>
+        )}
+
+        <div className={`text-xs mb-3 ${isDark ? 'text-white/40' : 'text-slate-400'}`}>
+          {selectedWords.length} Woerter · {sourceLang.toUpperCase()} → {targetLang.toUpperCase()}
+        </div>
+
+        <button
+          onClick={() => onCreateUnit(unitTitle, sourceLang, targetLang)}
+          disabled={isCreating || selectedWords.length === 0 || !unitTitle.trim()}
+          className={`w-full py-3 rounded-xl font-medium transition-all ${
+            selectedWords.length > 0 && unitTitle.trim()
+              ? 'bg-gradient-to-r from-blue-500 to-cyan-500 text-white hover:shadow-lg'
+              : isDark ? 'bg-white/5 text-white/30' : 'bg-slate-100 text-slate-400'
+          }`}
+        >
+          {isCreating ? 'Wird erstellt...' : 'Lernunit starten'}
+        </button>
+      </div>
+    </div>
+  )
+}