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/useTranslationSubmit.ts

@@ -143,6 +143,10 @@ export function useTranslationSubmit(): UseTranslationSubmitReturn {
       if (config.pdfMode) {
         formData.append('pdf_mode', config.pdfMode);
       }
+      // Glossary for LLM translation (Pro only)
+      if (config.glossaryId) {
+        formData.append('glossary_id', config.glossaryId);
+      }
 
       const token = localStorage.getItem('token');
       const headers: Record<string, string> = {};