Auto-mount defpages: eliminate Python route stubs across all 9 services

Defpages are now declared with absolute paths in .sx files and auto-mounted
directly on the Quart app, removing ~850 lines of blueprint mount_pages calls,
before_request hooks, and g.* wrapper boilerplate. A new page = one defpage
declaration, nothing else.

Infrastructure:
- async_eval awaits coroutine results from callable dispatch
- auto_mount_pages() mounts all registered defpages on the app
- g._defpage_ctx pattern passes helper data to layout context

Migrated: sx, account, orders, federation, cart, market, events, blog

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

cart/app.py

@@ -185,8 +185,6 @@ def create_app() -> "Quart":
     from sxc.pages import setup_cart_pages
     setup_cart_pages()
 
-    from shared.sx.pages import mount_pages
-
     # --- Blueprint registration ---
     # Static prefixes first, dynamic (page_slug) last
 
@@ -196,21 +194,22 @@ def create_app() -> "Quart":
         url_prefix="/",
     )
 
-    # Cart overview at GET /
+    # Cart overview blueprint (no defpage routes, just action endpoints)
     overview_bp = register_cart_overview(url_prefix="/")
-    mount_pages(overview_bp, "cart", names=["cart-overview"])
     app.register_blueprint(overview_bp, url_prefix="/")
 
-    # Page admin at /<page_slug>/admin/ (before page_cart catch-all)
+    # Page admin (PUT /payments/ etc.)
     admin_bp = register_page_admin()
-    mount_pages(admin_bp, "cart", names=["cart-admin", "cart-payments"])
     app.register_blueprint(admin_bp, url_prefix="/<page_slug>/admin")
 
-    # Page cart at /<page_slug>/ (dynamic, matched last)
+    # Page cart (POST /checkout/ etc.)
     page_cart_bp = register_page_cart(url_prefix="/")
-    mount_pages(page_cart_bp, "cart", names=["page-cart-view"])
     app.register_blueprint(page_cart_bp, url_prefix="/<page_slug>")
 
+    # Auto-mount all defpages with absolute paths
+    from shared.sx.pages import auto_mount_pages
+    auto_mount_pages(app, "cart")
+
     return app