fix: show target-language-specific translations in preview + rename migration

Two issues found in screenshot review:
1. Glossary preview always showed English 'target' field (foie → liver)
   instead of the language-specific translation. Now looks up
   term.translations[targetLang] first, falls back to term.target.
   When target is Persian, preview shows 'foie → کبد' (Persian).

2. Previous migration b7c8d9e0f1a2 was already applied on server before
   the rename was added. New migration c8d9e0f1a2b3 handles the rename
   separately: glossaries with target_language='multi' get their name
   changed from 'Anglais' to 'Multilingue'.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

alembic/versions/c8d9e0f1a2b3_rename_multilingual_glossaries.py

@@ -0,0 +1,40 @@
+"""Rename multilingual glossaries from 'Anglais' to 'Multilingue'
+
+Revision ID: c8d9e0f1a2b3
+Revises: b7c8d9e0f1a2
+Create Date: 2026-05-31
+
+Previous migration b7c8d9e0f1a2 set target_language='multi' but the rename
+part was added after the migration was already applied on the server.
+This migration handles the rename separately.
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers
+revision = "c8d9e0f1a2b3"
+down_revision = "b7c8d9e0f1a2"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Rename glossaries that are multilingual but still have "Anglais" in name
+    op.execute("""
+        UPDATE glossaries
+        SET name = REPLACE(name, 'Anglais', 'Multilingue')
+        WHERE target_language = 'multi'
+          AND name LIKE '%%Anglais%%'
+    """)
+
+
+def downgrade() -> None:
+    op.execute("""
+        UPDATE glossaries
+        SET name = REPLACE(name, 'Multilingue', 'Anglais')
+        WHERE target_language = 'multi'
+          AND name LIKE '%%Multilingue%%'
+    """)