Add full fediverse social service

Social blueprint with timeline, compose, search, follow/unfollow,
like/boost interactions, and notifications. Inbox handler extended
for Create/Update/Delete/Accept/Like/Announce with notification
creation. HTMX-powered infinite scroll and interaction buttons.
Nav updated with Timeline, Public, Search, and Notifications links.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bp/__init__.py

@@ -2,3 +2,4 @@ from .wellknown.routes import register as register_wellknown_bp
 from .actors.routes import register as register_actors_bp
 from .identity.routes import register as register_identity_bp
 from .auth.routes import register as register_auth_bp
+from .social.routes import register as register_social_bp