refactor: 5 architectural improvements (Tasks 2-5 + Task 6 fix)

- feat(domain): Hashtag value object with canonical extract() — unifies two
  divergent private implementations; fields pre-compute raw/normalized/url_slug/ap_name

- feat(presentation): Deps<S: FromAppState> extractor — each handler now
  declares its exact dependency surface; AppState unchanged; handlers
  become unit-testable without mocking all 20 deps

- refactor(feed): replace 5 flat FeedRepository methods with FeedQuery/FeedScope
  — single query() method; SQL shared logic lives once; adding feed types
  no longer requires 5 edits

- refactor(activitypub): ActivityPubRepository + OutboundFederationPort moved
  out of domain::ports into activitypub-base::ap_ports — domain crate no
  longer knows about AP IDs, inboxes, or actor URLs

- fix(outbox): OutboxRelay now opens a per-row transaction so FOR UPDATE
  SKIP LOCKED actually holds the lock during publish + mark_delivered

crates/adapters/activitypub/src/handler.rs

@@ -9,8 +9,8 @@ use url::Url;
 
 use crate::note::ThoughtNote;
 use crate::urls::ThoughtsUrls;
-use activitypub_base::ApObjectHandler;
-use domain::ports::{ActivityPubRepository, EventPublisher};
+use activitypub_base::{ActivityPubRepository, ApObjectHandler};
+use domain::ports::EventPublisher;
 use domain::value_objects::UserId;
 
 pub struct ThoughtsObjectHandler {