Migrate all apps to defpage declarative page routes

Replace Python GET page handlers with declarative defpage definitions in .sx
files across all 8 apps (sx docs, orders, account, market, cart, federation,
events, blog). Each app now has sxc/pages/ with setup functions, layout
registrations, page helpers, and .sx defpage declarations.

Core infrastructure: add g I/O primitive, PageDef support for auth/layout/
data/content/filter/aside/menu slots, post_author auth level, and custom
layout registration. Remove ~1400 lines of render_*_page/render_*_oob
boilerplate. Update all endpoint references in routes, sx_components, and
templates to defpage_* naming.

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

events/bp/slots/routes.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from quart import (
-    request, render_template, make_response, Blueprint, g, jsonify
+    request, Blueprint, g, jsonify
 )
 
 from sqlalchemy.exc import IntegrityError
@@ -19,21 +19,16 @@ from shared.browser.app.utils import (
     parse_time,
     parse_cost
 )
-from shared.browser.app.utils.htmx import is_htmx_request
 from shared.sx.helpers import sx_response
 
 
 def register():
     bp = Blueprint("slots", __name__, url_prefix='/slots')
-    
-    # ---------- Pages ----------
-    
+
     bp.register_blueprint(
         register_slot()
     )
 
-
-
     @bp.context_processor
     async def get_slots():
       calendar = getattr(g, "calendar", None)
@@ -43,19 +38,17 @@ def register():
           }
       return {"slots": []}
 
-    @bp.get("/")
-    async def get(**kwargs):
-        from shared.sx.page import get_template_context
-        from sx.sx_components import render_slots_page, render_slots_oob
-
-        tctx = await get_template_context()
-        if not is_htmx_request():
-            html = await render_slots_page(tctx)
-            return await make_response(html)
-        else:
-            sx_src = await render_slots_oob(tctx)
-            return sx_response(sx_src)
+    @bp.before_request
+    async def _prepare_page_data():
+        if "defpage_" not in (request.endpoint or ""):
+            return
+        calendar = getattr(g, "calendar", None)
+        slots = await svc_list_slots(g.s, calendar.id) if calendar else []
+        from sx.sx_components import render_slots_table
+        g.slots_content = render_slots_table(slots, calendar)
 
+    from shared.sx.pages import mount_pages
+    mount_pages(bp, "events", names=["slots-listing"])
 
     @bp.post("/")
     @require_admin