feat(ap): ActivityPub spec compliance and profile completeness

Phase 1 — spec compliance:
- Add AS_PUBLIC constant; add to/cc fields to CreateActivity, DeleteActivity,
  UpdateActivity, AddActivity; populate on all broadcast call sites
- Add @context to outbox CreateActivity items
- Set manuallyApprovesFollowers: true to match actual Pending follow flow
- Gate PermissiveVerifier behind FEDERATION_DEBUG env var
- Add updated timestamp to Person actor JSON
- Improve actor update delivery logging

Phase 2a Batch 1 — AP layer:
- Add /inbox shared inbox route; add endpoints.sharedInbox to Person
- Paginate followers and following collections (20/page, OrderedCollectionPage)

Phase 2a Batch 2 — profile completeness:
- DB migrations: banner_path, also_known_as columns; user_profile_fields table
- ProfileField value object; UserProfileFieldsRepository port
- Banner image upload (stored via image-converter, surfaced as image in Person)
- alsoKnownAs field in Person (account migration support)
- Custom profile fields (up to 4 PropertyValue attachments in Person)
- Profile settings UI: banner preview/upload, alsoKnownAs input, fields form
- PUT /api/v1/profile/fields API endpoint

crates/presentation/src/routes.rs

@@ -223,6 +223,7 @@ fn api_routes(rate_limit: u64) -> Router<AppState> {
         .route("/import/profiles", routing::get(handlers::import::api_get_profiles).post(handlers::import::api_post_profile))
         .route("/import/profiles/{id}", routing::delete(handlers::import::api_delete_profile))
         .route("/profile", routing::get(handlers::api::get_profile).put(handlers::api::update_profile_handler))
+        .route("/profile/fields", routing::put(handlers::api::update_profile_fields_handler))
         .route("/search", routing::get(handlers::api::get_search))
         .route("/people/{id}", routing::get(handlers::api::get_person_handler))
         .route("/people/{id}/credits", routing::get(handlers::api::get_person_credits_handler))