README: replace vague cross-app section with actual code dependencies

List specific model imports, glue services, and internal APIs
that events code actually references. Remove descriptions of what
other apps do to events data (that belongs in those apps' docs).

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

README.md

@@ -59,13 +59,20 @@ All events-domain models live in `models/calendars.py`:
 
 `order_id` on CalendarEntry and Ticket is a plain integer column — no FK constraint to the orders table. The cart app writes these values via glue services (`order_lifecycle.py`), not directly.
 
-## Cross-App Integration
+## Dependencies
 
-- **Cart checkout:** The cart app marks entries as "ordered" and sets `order_id` via `glue/services/order_lifecycle.py`.
-- **Payment confirmation:** Cart app marks entries as "provisional" via the same glue service.
-- **Login adoption:** Anonymous entries are adopted to the logged-in user via `glue/services/cart_adoption.py`.
-- **Internal API:** `/internal/events/` endpoints serve calendar data to other apps.
-- **Cart widget:** Context processor fetches cart summary via internal API.
+**Cross-app model imports:**
+- `blog.models.ghost_content.Post` — `app.py` context processor, calendar/market services for page hydration
+- `market.models.market_place.MarketPlace` — `app.py` context processor, marketplace views
+- `cart.models.page_config.PageConfig` — `bp/payments/routes.py` for per-page SumUp config
+
+**Glue services:**
+- `glue.services.relationships.attach_child / detach_child` — calendar and marketplace services manage page associations
+- `glue.services.navigation.get_navigation_tree` — context processor builds site nav
+
+**Internal APIs:**
+- Calls `GET /internal/cart/summary` — context processor for cart widget
+- Exposes `/internal/events/*` via `events_api.py` — serves calendar data to other apps
 
 ## Migrations