feat(federation): enrich RemoteActor with bio, banner, followers/following URLs

Bumps k-ap to 0.3.1 which adds bio, banner_url, followers_url,
following_url, and also_known_as to RemoteActor. These are populated
from fetched actor JSON at follow/ingest time so followers and following
listings no longer return null profile fields.

Adds migration 015 for the new remote_actors columns, updates all JOIN
queries in postgres-federation to select and return the new fields, and
maps them through k_ap_actor_to_domain.

Also fixes clippy: remove empty line after doc comment in port.rs.

crates/adapters/postgres/migrations/015_remote_actors_rich_fields.sql

@@ -0,0 +1,6 @@
+ALTER TABLE remote_actors
+    ADD COLUMN IF NOT EXISTS bio           TEXT,
+    ADD COLUMN IF NOT EXISTS banner_url    TEXT,
+    ADD COLUMN IF NOT EXISTS followers_url TEXT,
+    ADD COLUMN IF NOT EXISTS following_url TEXT,
+    ADD COLUMN IF NOT EXISTS also_known_as TEXT[];