fix(federation): fix 27 AP bugs, gaps, and inconsistencies

Round 1 — 18 bug fixes:
- remote likes/boosts now persist in engagement tables
- intern_remote_actor uses name@domain, expanded username to VARCHAR(255)
- PgRemoteActorRepository upsert/find now handles all fields
- update_following_status no longer a no-op, count_followers counts all
- accept/reject follow publishes event before DB mark (atomicity)
- fetch_outbox_page follows pagination via next links
- actor URL canonicalized to /users/{uuid}
- content_to_html escapes single quotes
- WebFinger accepts application/ld+json type
- try_from_ap accepts Article and Page object types
- feed SQL uses parameterized viewer UUID instead of format!
- content cap raised from 500 to 5000 chars
- also_known_as changed from Option<String> to Vec<String>
- connections fetch always triggers from page 1

Round 2 — 9 gap fixes:
- on_announce_removed handler deletes boost row on Undo(Announce)
- on_update handles Person/Service/Group actor profile updates
- sync_remote_actor_to_user syncs remote_actors → users on create/update
- FederationBlockPort: block_by_username sends Block activity to remote
- domain RemoteActor gains inbox_url, shared_inbox_url fields
- remote_actors attachment column (JSONB) with read/write
- .well-known/host-meta endpoint
- 256KB body limit on AP inbox routes
- outbox cleanup job (7-day retention, hourly sweep)

crates/presentation/src/handlers/well_known.rs

@@ -0,0 +1,20 @@
+use axum::{extract::State, http::header, response::IntoResponse};
+
+use crate::state::AppState;
+
+pub async fn host_meta(State(state): State<AppState>) -> impl IntoResponse {
+    let domain = url::Url::parse(&state.base_url)
+        .ok()
+        .and_then(|u| u.host_str().map(|s| s.to_string()))
+        .unwrap_or_default();
+    let body = format!(
+        r#"<?xml version="1.0" encoding="UTF-8"?>
+<XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0">
+  <Link rel="lrdd" template="https://{domain}/.well-known/webfinger?resource={{uri}}"/>
+</XRD>"#
+    );
+    (
+        [(header::CONTENT_TYPE, "application/xrd+xml; charset=utf-8")],
+        body,
+    )
+}