feat: add multilingual glossary support (backend + frontend types)

Backend:
- Add source_language column to glossaries table
- Add translations JSON column to glossary_terms table
- Alembic migration for schema changes
- format_glossary_for_prompt now language-aware: extracts correct
  translation per target language, falls back to EN reference for
  templates with only FR→EN data
- CRUD routes accept/return source_language and translations
- Pydantic schemas updated

Frontend:
- Types updated: GlossaryTerm now has translations: Record<string, string>
- Glossary/GlossaryListItem now have source_language
- Added SUPPORTED_LANGUAGES constant (13 languages)

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

alembic/versions/d4a1f8e2b3c7_add_glossary_multilingual.py

@@ -0,0 +1,35 @@
+"""Add multilingual support to glossaries
+
+Revision ID: d4a1f8e2b3c7
+Revises: cb71a958ad92
+Create Date: 2026-05-16
+
+Adds source_language to glossaries and translations JSON to glossary_terms.
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers
+revision = "d4a1f8e2b3c7"
+down_revision = "cb71a958ad92"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "glossaries",
+        sa.Column("source_language", sa.String(10), nullable=False, server_default="fr"),
+    )
+    op.add_column(
+        "glossary_terms",
+        sa.Column("translations", sa.JSON, nullable=True),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("glossary_terms", "translations")
+    op.drop_column("glossaries", "source_language")