feat: per-entity federation privacy toggles for reviews and watchlist

- add federate_reviews + federate_watchlist to UserSettings (default true)
- new UserFederationSettingsQuery port with FederationFlags struct
- remove get_user_federate_goals from LocalApContentQuery
- gate ReviewLogged, ReviewUpdated, WatchlistEntryAdded, on_poster_synced on flags
- goals gating migrated to UserFederationSettingsQuery
- ReviewDeleted and WatchlistEntryRemoved ungated (tombstones always fire)
- sqlite + postgres migrations and adapter impls
- settings API and SPA toggles

crates/adapters/postgres/migrations/0028_federation_privacy.sql

@@ -0,0 +1,2 @@
+ALTER TABLE user_settings ADD COLUMN federate_reviews BOOLEAN NOT NULL DEFAULT TRUE;
+ALTER TABLE user_settings ADD COLUMN federate_watchlist BOOLEAN NOT NULL DEFAULT TRUE;