chore(api): fix Alembic offline migration compatibility (#24795)

This PR fixes Alembic offline mode (`--sql` flag) by ensuring data migration functions only execute in online mode. When running in offline mode, these functions now skip data operations and output informational comments to the generated SQL.

.github/workflows/db-migration-test.yml

@@ -34,6 +34,12 @@ jobs:
 
       - name: Install dependencies
         run: uv sync --project api
+      - name: Ensure Offline migration are supported
+        run: |
+          # upgrade
+          uv run --directory api flask db upgrade 'base:head' --sql
+          # downgrade
+          uv run --directory api flask db downgrade 'head:base' --sql
 
       - name: Prepare middleware env
         run: |