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>

federation/sxc/pages/social.sx

@@ -1,49 +1,49 @@
 ;; Federation social pages
 
 (defpage home-timeline
-  :path "/"
+  :path "/social/"
   :auth :login
   :layout :social
   :content (home-timeline-content))
 
 (defpage public-timeline
-  :path "/public"
+  :path "/social/public"
   :auth :public
   :layout :social
   :content (public-timeline-content))
 
 (defpage compose-form
-  :path "/compose"
+  :path "/social/compose"
   :auth :login
   :layout :social
   :content (compose-content))
 
 (defpage search
-  :path "/search"
+  :path "/social/search"
   :auth :public
   :layout :social
   :content (search-content))
 
 (defpage following-list
-  :path "/following"
+  :path "/social/following"
   :auth :login
   :layout :social
   :content (following-content))
 
 (defpage followers-list
-  :path "/followers"
+  :path "/social/followers"
   :auth :login
   :layout :social
   :content (followers-content))
 
 (defpage actor-timeline
-  :path "/actor/<int:id>"
+  :path "/social/actor/<int:id>"
   :auth :public
   :layout :social
-  :content (actor-timeline-content))
+  :content (actor-timeline-content id))
 
 (defpage notifications
-  :path "/notifications"
+  :path "/social/notifications"
   :auth :login
   :layout :social
   :content (notifications-content))