feat: discoverability (NodeInfo, hashtags) and moderation (domain/actor blocking)

- NodeInfo at /.well-known/nodeinfo + /nodeinfo/2.0
- Hashtags #MoviesDiary + #MovieTitle on review posts; /tags/{tag} redirect
- Domain blocking: blocked_domains table, admin API + HTML, inbox enforcement
- Per-actor blocking: blocked_actors table, user API + HTML, BlockActivity send/receive
- Delivery filter excludes blocked actors and blocked-domain inboxes

crates/adapters/activitypub-base/src/content.rs

@@ -41,4 +41,7 @@ pub trait ApObjectHandler: Send + Sync {
 
     /// Actor unfollowed/was removed — clean up all their remote content.
     async fn on_actor_removed(&self, actor_url: &Url) -> anyhow::Result<()>;
+
+    /// Total number of locally-authored posts across all users.
+    async fn count_local_posts(&self) -> anyhow::Result<u64>;
 }