Phase 5: Replace HTTP cart adoption with event-driven adoption

Emit user.logged_in event instead of HTTP POST to /internal/cart/adopt.
Event is emitted inside the last_login_at transaction for atomicity.

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

bp/auth/routes.py

@@ -31,7 +31,7 @@ from shared.infrastructure.urls import coop_url
 from sqlalchemy.orm import selectinload
 from shared.browser.app.redis_cacher import clear_cache
 from shared.infrastructure.cart_identity import current_cart_identity
-from shared.infrastructure.internal_api import post as api_post
+from shared.events import emit_event
 from .services import pop_login_redirect_target, store_login_redirect_target
 from .services.auth_operations import (
     get_app_host,
@@ -254,20 +254,23 @@ def register(url_prefix="/auth"):
                     u2 = await s.get(User, user_id)
                     if u2:
                         u2.last_login_at = now
-                    # s.begin() will commit on successful exit
+                    # Emit adoption event inside this transaction
+                    if anon_session_id:
+                        await emit_event(
+                            s,
+                            "user.logged_in",
+                            "user",
+                            user_id,
+                            {
+                                "user_id": user_id,
+                                "session_id": anon_session_id,
+                            },
+                        )
         except SQLAlchemyError:
             current_app.logger.exception(
                 "[auth] non-fatal DB update after Ghost upsert for user_id=%s", user_id
             )
 
-        # Adopt cart + calendar entries via cart app internal API
-        if anon_session_id:
-            await api_post(
-                "cart",
-                "/internal/cart/adopt",
-                json={"user_id": user_id, "session_id": anon_session_id},
-            )
-
         # ---- Finalize login ----
         qsession[SESSION_USER_KEY] = user_id