feat: multilingual glossary UI, translate selector, context fusion

- TermEditor: rewritten with expandable multilingual translation grid
  (13 languages), editorial styling, source/target + translations JSON
- GlossarySelector: new component in translate page config panel,
  fetches user glossaries, shows flag + term count, Pro+LLM only
- useTranslationConfig: added glossaryId state
- useTranslationSubmit: sends glossary_id to backend
- Context page: removed textarea glossary, presets now create API
  glossaries via template import, added link to Glossaries page
- i18n: added 12 keys × 13 locales for glossary/translate/context

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/app/dashboard/translate/useTranslationConfig.ts

@@ -64,6 +64,7 @@ export function useTranslationConfig(hasFile: boolean): UseTranslationConfigRetu
   const [sourceLang, setSourceLang] = useState('auto');
   const [targetLang, setTargetLang] = useState(settings.defaultTargetLanguage || '');
   const [provider, setProvider] = useState<Provider | null>(null);
+  const [glossaryId, setGlossaryId] = useState<string | null>(null);
   const [availableProviders, setAvailableProviders] = useState<AvailableProvider[]>([]);
   const [isLoadingProviders, setIsLoadingProviders] = useState(false);
   const [languages, setLanguages] = useState<Language[]>([]);
@@ -212,7 +213,8 @@ export function useTranslationConfig(hasFile: boolean): UseTranslationConfigRetu
     targetLang,
     mode,
     provider: provider ?? undefined,
-  }), [sourceLang, targetLang, mode, provider]);
+    glossaryId,
+  }), [sourceLang, targetLang, mode, provider, glossaryId]);
 
   return {
     sourceLang,
@@ -229,6 +231,8 @@ export function useTranslationConfig(hasFile: boolean): UseTranslationConfigRetu
     setSourceLang,
     setTargetLang,
     setProvider,
+    glossaryId,
+    setGlossaryId,
     getConfig,
   };
 }