Decouple all cross-app service calls to HTTP endpoints

Replace every direct cross-app services.* call with HTTP-based
communication: call_action() for writes, fetch_data() for reads.
Each app now registers only its own domain service.

Infrastructure:
- shared/infrastructure/actions.py — POST client for /internal/actions/
- shared/infrastructure/data_client.py — GET client for /internal/data/
- shared/contracts/dtos.py — dto_to_dict/dto_from_dict serialization

Action endpoints (writes):
- events: 8 handlers (ticket adjust, claim/confirm, toggle, adopt)
- market: 2 handlers (create/soft-delete marketplace)
- cart: 1 handler (adopt cart for user)

Data endpoints (reads):
- blog: 4 (post-by-slug/id, posts-by-ids, search-posts)
- events: 10 (pending entries/tickets, entries/tickets for page/order,
  entry-ids, associated-entries, calendars, visible-entries-for-period)
- market: 1 (marketplaces-for-container)
- cart: 1 (cart-summary)

Service registration cleanup:
- blog→blog+federation, events→calendar+federation,
  market→market+federation, cart→cart only,
  federation→federation only, account→nothing
- Stubs reduced to minimal StubFederationService

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

shared/events/handlers/login_handlers.py

@@ -1,23 +1,31 @@
 from __future__ import annotations
 
+import logging
+
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from shared.events import register_activity_handler
+from shared.infrastructure.actions import call_action, ActionError
 from shared.models.federation import APActivity
-from shared.services.registry import services
+
+log = logging.getLogger(__name__)
 
 
 async def on_user_logged_in(activity: APActivity, session: AsyncSession) -> None:
     data = activity.object_data
     user_id = data["user_id"]
     session_id = data["session_id"]
+    payload = {"user_id": user_id, "session_id": session_id}
 
-    if services.has("cart"):
-        await services.cart.adopt_cart_for_user(session, user_id, session_id)
-
-    if services.has("calendar"):
-        await services.calendar.adopt_entries_for_user(session, user_id, session_id)
-        await services.calendar.adopt_tickets_for_user(session, user_id, session_id)
+    for app, action in [
+        ("cart", "adopt-cart-for-user"),
+        ("events", "adopt-entries-for-user"),
+        ("events", "adopt-tickets-for-user"),
+    ]:
+        try:
+            await call_action(app, action, payload=payload)
+        except ActionError:
+            log.warning("Failed: %s/%s for user %s", app, action, user_id)
 
 
 register_activity_handler("rose:Login", on_user_logged_in)