perf: query generating 3D summaries for activity polls

[atomantic]

Summary

Activity polls now query only id/name columns for non-deleted generating image-to-3D models, avoiding full gallery JSONB hydration on every refresh. Update ordering, the name-or-id fallback, empty/error degradation, and the full gallery listing remain unchanged.

Test plan

• 138 focused service, generation-lifecycle, route, and database-guard tests passed.
• A PostgreSQL test on portos_test passed with 1,005 synthetic records: exactly two generating summaries returned in update order, with completed/draft/failed/deleted models excluded and full gallery records preserved.
• SQL assertion pins projection at the database boundary so SELECT * followed by JavaScript filtering cannot regress the optimization.

Closes #6690