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/user.rs

@@ -1,15 +1,18 @@
 use async_trait::async_trait;
+use url::Url;
 
 #[derive(Debug, Clone)]
 pub struct ApUser {
     pub id: uuid::Uuid,
     pub username: String,
     pub bio: Option<String>,
-    pub avatar_path: Option<String>,
+    pub avatar_url: Option<Url>,
+    pub profile_url: Option<Url>,
 }
 
 #[async_trait]
 pub trait ApUserRepository: Send + Sync {
     async fn find_by_id(&self, id: uuid::Uuid) -> anyhow::Result<Option<ApUser>>;
     async fn find_by_username(&self, username: &str) -> anyhow::Result<Option<ApUser>>;
+    async fn count_users(&self) -> anyhow::Result<usize>;
 }