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>

blog/app.py

@@ -162,6 +162,23 @@ def create_app() -> "Quart":
         )
         return jsonify(resp)
 
+    # Auto-mount all defpages with absolute paths
+    from shared.sx.pages import auto_mount_pages
+    auto_mount_pages(app, "blog")
+
+    # --- Pass defpage helper data to template context for layouts ---
+    @app.context_processor
+    async def inject_blog_data():
+        import os
+        from shared.config import config as get_config
+        ctx = {
+            "blog_title": get_config()["blog_title"],
+            "base_title": get_config()["title"],
+            "unsplash_api_key": os.environ.get("UNSPLASH_ACCESS_KEY", ""),
+        }
+        ctx.update(getattr(g, '_defpage_ctx', {}))
+        return ctx
+
     # --- debug: url rules ---
     @app.get("/__rules")
     async def dump_rules():