feat: prevent duplicate glossary presets + fix i18n source warning bug

- Add template_id column to Glossary model (nullable, indexed)
- Backend: return 409 Conflict if user already imported a template
- Frontend: disable preset cards already imported, show 'Imported' badge
- Fix duplicated text in GlossarySelector source warning (hardcoded FR text removed)
- Complete i18n migration for glossaries page and GlossarySelector
- Add glossaries.presets.alreadyImported key in all 13 locales

routes/glossary_routes.py

@@ -58,6 +58,7 @@ def _format_glossary(glossary: Glossary) -> dict:
         "name": glossary.name,
         "source_language": glossary.source_language,
         "target_language": getattr(glossary, "target_language", "multi") or "multi",
+        "template_id": getattr(glossary, "template_id", None),
         "terms": [_format_term(t) for t in glossary.terms] if glossary.terms else [],
         "created_at": glossary.created_at.isoformat() if glossary.created_at else None,
         "updated_at": glossary.updated_at.isoformat() if glossary.updated_at else None,
@@ -591,13 +592,30 @@ async def import_glossary_template(
             )
         
         glossary_name = name or template_data.get("name", template_info.get("name", template_id))
-        
+
         with get_sync_session() as session:
+            # Check if user already imported this template
+            existing = (
+                session.query(Glossary)
+                .filter_by(user_id=user.id, template_id=template_id)
+                .first()
+            )
+            if existing:
+                return JSONResponse(
+                    status_code=409,
+                    content={
+                        "error": "TEMPLATE_ALREADY_IMPORTED",
+                        "message": f"You already have a glossary from the '{template_id}' template.",
+                        "data": _format_glossary(existing),
+                    },
+                )
+
             glossary = Glossary(
                 user_id=user.id,
                 name=glossary_name,
                 source_language=template_info.get("source_lang", template_data.get("source_lang", "fr")),
                 target_language=template_info.get("target_lang", template_data.get("target_lang", "multi")),
+                template_id=template_id,
                 created_at=datetime.now(timezone.utc),
                 updated_at=datetime.now(timezone.utc),
             )