- Register 'linkedin' FeatureGroup with routers.linkedin and
api.linkedin_image_generation routers
- Register 'facebook' FeatureGroup with
api.facebook_writer.routers:facebook_router
- Add 'linkedin' and 'facebook' profiles to PROFILE_GROUP_MAP
- Remove dead imports of linkedin_router, linkedin_image_router,
and facebook_router from app.py (router manager handles via
CORE_ROUTER_REGISTRY)
- Add LINKEDIN and FACEBOOK keys to frontend FEATURE_KEYS
- Add route priorities for /linkedin-writer and /facebook-writer
- Change route gates from feature='social' to feature='linkedin'
and feature='facebook' respectively