Unify domain_events + ap_activities into AP-shaped event bus

All cross-service events now flow through ap_activities with a unified
EventProcessor. Internal events use visibility="internal"; federation
activities use visibility="public" and get delivered by a wildcard handler.

- Add processing columns to APActivity (process_state, actor_uri, etc.)
- New emit_activity() / register_activity_handler() API
- EventProcessor polls ap_activities instead of domain_events
- Rewrite all handlers to accept APActivity
- Migrate all 7 emit_event call sites to emit_activity
- publish_activity() sets process_state=pending directly (no emit_event bridge)
- Migration to drop domain_events table

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

events/handlers/ap_delivery_handler.py

@@ -1,7 +1,7 @@
 """Deliver AP activities to remote followers.
 
-On ``federation.activity_created`` → load activity + actor + followers →
-sign with HTTP Signatures → POST to each follower inbox.
+Registered as a wildcard handler — fires for every activity.  Skips
+non-public activities and those without an actor profile.
 """
 from __future__ import annotations
 
@@ -11,7 +11,7 @@ import httpx
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from shared.events.bus import register_handler, DomainEvent
+from shared.events.bus import register_activity_handler
 from shared.models.federation import ActorProfile, APActivity, APFollower
 from shared.services.registry import services
 
@@ -33,12 +33,9 @@ def _build_activity_json(activity: APActivity, actor: ActorProfile, domain: str)
     object_id = activity.activity_id + "/object"
 
     if activity.activity_type == "Delete":
-        # Delete: object is a Tombstone with just id + type
         obj.setdefault("id", object_id)
         obj.setdefault("type", "Tombstone")
     else:
-        # Create/Update: full object with attribution
-        # Prefer stable id from object_data (set by try_publish), fall back to activity-derived
         obj.setdefault("id", object_id)
         obj.setdefault("type", activity.object_type)
         obj.setdefault("attributedTo", actor_url)
@@ -105,30 +102,20 @@ async def _deliver_to_inbox(
         return False
 
 
-async def on_activity_created(event: DomainEvent, session: AsyncSession) -> None:
-    """Deliver a newly created activity to all followers."""
+async def on_any_activity(activity: APActivity, session: AsyncSession) -> None:
+    """Deliver a public activity to all followers of its actor."""
     import os
 
+    # Only deliver public activities that have an actor profile
+    if activity.visibility != "public":
+        return
+    if activity.actor_profile_id is None:
+        return
     if not services.has("federation"):
         return
 
-    payload = event.payload
-    activity_id_uri = payload.get("activity_id")
-    if not activity_id_uri:
-        return
-
     domain = os.getenv("AP_DOMAIN", "rose-ash.com")
 
-    # Load the activity
-    activity = (
-        await session.execute(
-            select(APActivity).where(APActivity.activity_id == activity_id_uri)
-        )
-    ).scalar_one_or_none()
-    if not activity:
-        log.warning("Activity not found: %s", activity_id_uri)
-        return
-
     # Load actor with private key
     actor = (
         await session.execute(
@@ -136,7 +123,7 @@ async def on_activity_created(event: DomainEvent, session: AsyncSession) -> None
         )
     ).scalar_one_or_none()
     if not actor or not actor.private_key_pem:
-        log.warning("Actor not found or missing key for activity %s", activity_id_uri)
+        log.warning("Actor not found or missing key for activity %s", activity.activity_id)
         return
 
     # Load followers
@@ -147,14 +134,13 @@ async def on_activity_created(event: DomainEvent, session: AsyncSession) -> None
     ).scalars().all()
 
     if not followers:
-        log.debug("No followers to deliver to for %s", activity_id_uri)
+        log.debug("No followers to deliver to for %s", activity.activity_id)
         return
 
     # Build activity JSON
     activity_json = _build_activity_json(activity, actor, domain)
 
-    # Deliver to each follower inbox
-    # Deduplicate inboxes (multiple followers might share a shared inbox)
+    # Deduplicate inboxes
     inboxes = {f.follower_inbox for f in followers if f.follower_inbox}
 
     log.info(
@@ -167,4 +153,5 @@ async def on_activity_created(event: DomainEvent, session: AsyncSession) -> None
             await _deliver_to_inbox(client, inbox_url, activity_json, actor, domain)
 
 
-register_handler("federation.activity_created", on_activity_created)
+# Wildcard: fires for every activity
+register_activity_handler("*", on_any_activity)