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>

events/bp/slot/routes.py

@@ -29,27 +29,6 @@ from shared.sx.helpers import sx_response
 def register():
     bp = Blueprint("slot", __name__, url_prefix='/<int:slot_id>')
 
-    @bp.before_request
-    async def _prepare_page_data():
-        if "defpage_" not in (request.endpoint or ""):
-            return
-        slot_id = (request.view_args or {}).get("slot_id")
-        slot = await svc_get_slot(g.s, slot_id) if slot_id else None
-        if not slot:
-            from quart import abort
-            abort(404)
-        g.slot = slot
-        calendar = getattr(g, "calendar", None)
-        from sx.sx_components import render_slot_main_panel
-        g.slot_content = render_slot_main_panel(slot, calendar)
-
-    @bp.context_processor
-    async def _inject_slot():
-        return {"slot": getattr(g, "slot", None)}
-
-    from shared.sx.pages import mount_pages
-    mount_pages(bp, "events", names=["slot-detail"])
-
     @bp.get("/edit/")
     @require_admin
     async def get_edit(slot_id: int, **kwargs):