feat(glossaries): add target_language support - DB migration, API, and UI language pair display

alembic/versions/e5b2c9d1f4a8_add_target_language_to_glossaries.py

@@ -0,0 +1,30 @@
+"""Add target_language to glossaries
+
+Revision ID: e5b2c9d1f4a8
+Revises: d4a1f8e2b3c7
+Create Date: 2026-05-31
+
+Adds target_language column to glossaries table.
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers
+revision = "e5b2c9d1f4a8"
+down_revision = "d4a1f8e2b3c7"
+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("target_language", sa.String(10), nullable=True, server_default="en"),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("glossaries", "target_language")