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/sqlite/migrations/0012_blocked_domains.sql

@@ -0,0 +1,5 @@
+CREATE TABLE blocked_domains (
+    domain     TEXT PRIMARY KEY,
+    reason     TEXT,
+    blocked_at TEXT NOT NULL
+);