Route outbound Follow through EventProcessor for retry

send_follow now emits a Follow activity via emit_activity() instead of
inline HTTP POST. New ap_follow_handler delivers to the remote inbox;
EventProcessor retries on failure. Wildcard delivery handler skips
Follow type to avoid duplicate broadcast.

Also add /social/ index page to per-app social blueprint.

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

shared/services/federation_impl.py

@@ -686,42 +686,21 @@ class SqlFederationService:
         session.add(follow)
         await session.flush()
 
-        # Send Follow activity
-        domain = _domain()
-        actor_url = f"https://{domain}/users/{local_username}"
-        follow_id = f"{actor_url}/activities/{uuid.uuid4()}"
-
-        follow_activity = {
-            "@context": "https://www.w3.org/ns/activitystreams",
-            "id": follow_id,
-            "type": "Follow",
-            "actor": actor_url,
-            "object": remote_actor_url,
-        }
-
-        import json
-        import httpx
-        from shared.utils.http_signatures import sign_request
-        from urllib.parse import urlparse
-
-        body_bytes = json.dumps(follow_activity).encode()
-        parsed = urlparse(remote.inbox_url)
-        headers = sign_request(
-            private_key_pem=actor.private_key_pem,
-            key_id=f"{actor_url}#main-key",
-            method="POST",
-            path=parsed.path,
-            host=parsed.netloc,
-            body=body_bytes,
+        # Emit Follow activity — EventProcessor delivers with retries
+        from shared.events.bus import emit_activity
+        await emit_activity(
+            session,
+            activity_type="Follow",
+            actor_uri=f"https://{_domain()}/users/{local_username}",
+            object_type="Actor",
+            object_data={
+                "target_inbox": remote.inbox_url,
+                "target_actor_url": remote_actor_url,
+                "following_id": follow.id,
+            },
+            visibility="public",
+            actor_profile_id=actor.id,
         )
-        headers["Content-Type"] = "application/activity+json"
-
-        try:
-            async with httpx.AsyncClient(timeout=15) as client:
-                await client.post(remote.inbox_url, content=body_bytes, headers=headers)
-        except Exception:
-            import logging
-            logging.getLogger(__name__).exception("Failed to send Follow to %s", remote.inbox_url)
 
     async def get_following(
         self, session: AsyncSession, username: str,