Add fediverse social features: followers/following lists, actor timelines

Adds get_followers_paginated and get_actor_timeline to FederationService
protocol + SQL implementation + stubs. Includes accumulated federation
changes: models, DTOs, delivery handler, webfinger, inline publishing,
widget nav templates, and migration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

models/__init__.py

@@ -29,4 +29,5 @@ from .container_relation import ContainerRelation
 from .menu_node import MenuNode
 from .federation import (
     ActorProfile, APActivity, APFollower, APInboxItem, APAnchor, IPFSPin,
+    RemoteActor, APFollowing, APRemotePost, APLocalPost, APInteraction, APNotification,
 )