feat: TranslationHub, Pair-Review-Button (Action-Bar), reviewed für Bilder

- TranslationHub (/translations): Coverage-Matrix, Batch-Übersetzen pro Tabelle×Sprache
- Pair Status: StatusSelect ersetzt durch Action-Bar ✓Reviewed/↩Draft/🚫Block,
  Reviewed kaskadiert via /pairs/:id/review (Backend prüft 3-Sprachen-Vollständigkeit)
- Top-Nav: 'Übersetzungen' zwischen Inhalte und Audio
- Dashboard: Übersetzungen-Kachel
- tables.js: pictures-Status um 'reviewed' erweitert

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/App.jsx

@@ -10,6 +10,7 @@ import AudioHub from './pages/AudioHub';
 import WordGenerator from './pages/WordGenerator';
 import Publish from './pages/Publish';
 import Settings from './pages/Settings';
+import TranslationHub from './pages/TranslationHub';
 
 function RequireAuth({ children }) {
   const user = getUser();
@@ -28,6 +29,7 @@ export default function App() {
         <Route path="/content" element={<RequireAuth><ContentHub /></RequireAuth>} />
         <Route path="/content/creation" element={<RequireAuth><ContentCreation /></RequireAuth>} />
         <Route path="/audio" element={<RequireAuth><AudioHub /></RequireAuth>} />
+        <Route path="/translations" element={<RequireAuth><TranslationHub /></RequireAuth>} />
         <Route path="/content/words" element={<RequireAuth><WordGenerator /></RequireAuth>} />
         <Route path="/publish" element={<RequireAuth><Publish /></RequireAuth>} />
         <Route path="/settings" element={<RequireAuth><Settings /></RequireAuth>} />