fix: Restore all files lost during destructive rebase

A previous `git pull --rebase origin main` dropped 177 local commits,
losing 3400+ files across admin-v2, backend, studio-v2, website,
klausur-service, and many other services. The partial restore attempt
(660295e2) only recovered some files.

This commit restores all missing files from pre-rebase ref 98933f5e
while preserving post-rebase additions (night-scheduler, night-mode UI,
NightModeWidget dashboard integration).

Restored features include:
- AI Module Sidebar (FAB), OCR Labeling, OCR Compare
- GPU Dashboard, RAG Pipeline, Magic Help
- Klausur-Korrektur (8 files), Abitur-Archiv (5+ files)
- Companion, Zeugnisse-Crawler, Screen Flow
- Full backend, studio-v2, website, klausur-service
- All compliance SDKs, agent-core, voice-service
- CI/CD configs, documentation, scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

studio-v2/lib/LanguageContext.tsx

@@ -0,0 +1,90 @@
+'use client'
+
+import { createContext, useContext, useState, useEffect, ReactNode } from 'react'
+import {
+  Language,
+  defaultLanguage,
+  getStoredLanguage,
+  setStoredLanguage,
+  translations,
+  availableLanguages,
+  isRTL,
+} from './i18n'
+
+interface LanguageContextType {
+  language: Language
+  setLanguage: (lang: Language) => void
+  t: (key: string) => string
+  isRTL: boolean
+  availableLanguages: typeof availableLanguages
+}
+
+const LanguageContext = createContext<LanguageContextType | null>(null)
+
+export function LanguageProvider({ children }: { children: ReactNode }) {
+  const [language, setLanguageState] = useState<Language>(defaultLanguage)
+  const [mounted, setMounted] = useState(false)
+
+  // Nach dem ersten Render: Sprache aus localStorage laden
+  useEffect(() => {
+    const stored = getStoredLanguage()
+    setLanguageState(stored)
+    setMounted(true)
+  }, [])
+
+  // Sprache setzen und speichern
+  const setLanguage = (lang: Language) => {
+    setLanguageState(lang)
+    setStoredLanguage(lang)
+    // Optional: document.dir fuer RTL setzen
+    if (typeof document !== 'undefined') {
+      document.documentElement.dir = isRTL(lang) ? 'rtl' : 'ltr'
+      document.documentElement.lang = lang
+    }
+  }
+
+  // Uebersetzungsfunktion
+  const t = (key: string): string => {
+    return translations[language][key] || translations[defaultLanguage][key] || key
+  }
+
+  // Waehrend SSR: Default anzeigen
+  if (!mounted) {
+    return (
+      <LanguageContext.Provider
+        value={{
+          language: defaultLanguage,
+          setLanguage: () => {},
+          t: (key) => translations[defaultLanguage][key] || key,
+          isRTL: false,
+          availableLanguages,
+        }}
+      >
+        {children}
+      </LanguageContext.Provider>
+    )
+  }
+
+  return (
+    <LanguageContext.Provider
+      value={{
+        language,
+        setLanguage,
+        t,
+        isRTL: isRTL(language),
+        availableLanguages,
+      }}
+    >
+      {children}
+    </LanguageContext.Provider>
+  )
+}
+
+// Hook fuer einfache Verwendung
+export function useLanguage() {
+  const context = useContext(LanguageContext)
+  if (!context) {
+    throw new Error('useLanguage must be used within a LanguageProvider')
+  }
+  return context
+}