Implements user profile data model and own-profile management endpoints:
- Profile and ProfileFavorites models in backend/app/models/profile.py
- Migration 0010_add_profile_tables.py (profiles, profile_favorites)
- Endpoints in backend/app/routers/profiles.py:
- GET /api/profile/me (own profile with default fallback)
- PUT /api/profile/me (upsert bio, avatar_asset_id, privacy settings)
- GET /api/profile/me/favorites (list favorite world IDs)
- PUT /api/profile/me/favorites (replace favorite world IDs)
- Fixes values_callable on Asset.asset_type ENUM in app/models/asset.py
- Added test_profile.py covering auth, validation, favorites, privacy
Independently re-verified: 19/19 new profile tests pass,
258/258 full backend regression suite passes with zero regressions.
