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>

events/bp/all_events/routes.py

@@ -15,6 +15,8 @@ from quart import Blueprint, g, request, render_template, render_template_string
 
 from shared.browser.app.utils.htmx import is_htmx_request
 from shared.infrastructure.cart_identity import current_cart_identity
+from shared.infrastructure.data_client import fetch_data
+from shared.contracts.dtos import CartSummaryDTO, PostDTO, dto_from_dict
 from shared.services.registry import services
 
 
@@ -47,8 +49,11 @@ def register() -> Blueprint:
                 if e.calendar_container_type == "page" and e.calendar_container_id
             })
             if post_ids:
-                posts = await services.blog.get_posts_by_ids(g.s, post_ids)
-                for p in posts:
+                raw_posts = await fetch_data("blog", "posts-by-ids",
+                                             params={"ids": ",".join(str(i) for i in post_ids)},
+                                             required=False) or []
+                for raw_p in raw_posts:
+                    p = dto_from_dict(PostDTO, raw_p)
                     page_info[p.id] = {"title": p.title, "slug": p.slug}
 
         return entries, has_more, pending_tickets, page_info
@@ -121,9 +126,13 @@ def register() -> Blueprint:
         entry = await services.calendar.entry_by_id(g.s, entry_id)
 
         # Updated cart count for OOB mini-cart
-        summary = await services.cart.cart_summary(
-            g.s, user_id=ident["user_id"], session_id=ident["session_id"],
-        )
+        summary_params = {}
+        if ident["user_id"] is not None:
+            summary_params["user_id"] = ident["user_id"]
+        if ident["session_id"] is not None:
+            summary_params["session_id"] = ident["session_id"]
+        raw_summary = await fetch_data("cart", "cart-summary", params=summary_params, required=False)
+        summary = dto_from_dict(CartSummaryDTO, raw_summary) if raw_summary else CartSummaryDTO()
         cart_count = summary.count + summary.calendar_count + summary.ticket_count
 
         # Render widget + OOB cart-mini