Add 'Alle zur Unit' button + fix topic display

Two buttons on topic cards:
- "Anzeigen": Shows words in search results (for review)
- "Alle zur Unit": Adds all topic words to the unit builder directly

Both buttons load from Kaikki and respect selected language.

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

studio-v2/app/vocabulary/page.tsx

@@ -238,9 +238,9 @@ export default function VocabularyPage() {
                       <span className={`text-sm font-semibold ${isDark ? 'text-cyan-300' : 'text-cyan-700'}`}>
                         💡 {topic.topic} ({topic.word_count})
                       </span>
+                      <div className="flex gap-2">
                         <button
                           onClick={async () => {
-                          // Load all words from this topic via Kaikki
                             setIsSearching(true)
                             const topicWords: VocabWord[] = []
                             for (const w of topic.words) {
@@ -253,11 +253,33 @@ export default function VocabularyPage() {
                             setResults(topicWords)
                             setIsSearching(false)
                           }}
+                          className={`text-xs px-3 py-1 rounded-lg ${isDark ? 'bg-white/10 text-white/60 hover:bg-white/20' : 'bg-slate-100 text-slate-600 hover:bg-slate-200'}`}
+                        >
+                          Anzeigen
+                        </button>
+                        <button
+                          onClick={async () => {
+                            setIsSearching(true)
+                            const topicWords: VocabWord[] = []
+                            for (const w of topic.words) {
+                              const r = await fetch(`${getApiBase()}/api/vocabulary/search?q=${encodeURIComponent(w)}&lang=en&limit=1&source=kaikki`)
+                              if (r.ok) {
+                                const d = await r.json()
+                                if (d.words?.[0] && !selectedWords.find(s => s.id === d.words[0].id)) {
+                                  topicWords.push(d.words[0])
+                                }
+                              }
+                            }
+                            setSelectedWords(prev => [...prev, ...topicWords])
+                            setResults(topicWords)
+                            setIsSearching(false)
+                          }}
                           className={`text-xs px-3 py-1 rounded-lg ${isDark ? 'bg-cyan-500/20 text-cyan-300 hover:bg-cyan-500/30' : 'bg-cyan-100 text-cyan-700 hover:bg-cyan-200'}`}
                         >
-                        Alle laden
+                          Alle zur Unit
                         </button>
                       </div>
+                    </div>
                     <div className="flex flex-wrap gap-1">
                       {(topic.display_words || topic.words).slice(0, 15).map((w: string, i: number) => (
                         <span key={i} className={`text-xs px-2 py-0.5 rounded-full ${isDark ? 'bg-white/5 text-white/50' : 'bg-slate-100 text-slate-500'}`}>{w}</span>