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

database/models.py

@@ -334,6 +334,7 @@ class Glossary(Base):
     name = Column(String(255), nullable=False)
     source_language = Column(String(10), nullable=False, default="fr")
     target_language = Column(String(10), nullable=True, default="en")
+    template_id = Column(String(50), nullable=True, index=True)
     created_at = Column(DateTime, default=_utcnow)
     updated_at = Column(DateTime, default=_utcnow, onupdate=_utcnow)
 
@@ -343,7 +344,10 @@ class Glossary(Base):
     )
 
     # Indexes
-    __table_args__ = (Index("ix_glossaries_user_id", "user_id"),)
+    __table_args__ = (
+        Index("ix_glossaries_user_id", "user_id"),
+        Index("ix_glossaries_template_id", "template_id"),
+    )
 
     def to_dict(self) -> dict:
         return {
@@ -352,6 +356,7 @@ class Glossary(Base):
             "name": self.name,
             "source_language": self.source_language,
             "target_language": self.target_language,
+            "template_id": self.template_id,
             "terms": [term.to_dict() for term in self.terms] if self.terms else [],
             "created_at": self.created_at.isoformat() if self.created_at else None,
             "updated_at": self.updated_at.isoformat() if self.updated_at else None,