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>

market/bp/browse/routes.py

@@ -5,17 +5,13 @@ from quart import (
     g,
     Blueprint,
     abort,
-    render_template,
-    render_template_string,
     make_response,
-    current_app,
 )
 from shared.config import config
 from .services.nav import category_context, get_nav
 from .services.blacklist.category import is_category_blocked
 
 from .services import (
-  _hx_fragment_request,
   _productInfo,
   _vary,
   _current_url_without_page,
@@ -33,27 +29,9 @@ def register():
     register_product(),
   )
 
-  @browse_bp.get("/")
-  @cache_page(tag="browse")
-  async def home():
-      """
-      Market landing page.
-      Uses the post data hydrated by the app-level before_request (g.post_data).
-      """
-      p_data = getattr(g, "post_data", None) or {}
-
-      # Determine which template to use based on request type
-      from shared.sx.page import get_template_context
-      from sx.sx_components import render_market_home_page, render_market_home_oob
-
-      ctx = await get_template_context()
-      ctx.update(p_data)
-      if not is_htmx_request():
-          html = await render_market_home_page(ctx)
-          return await make_response(html)
-      else:
-          sx_src = await render_market_home_oob(ctx)
-          return sx_response(sx_src)
+  # Mount defpage for market home (GET /)
+  from shared.sx.pages import mount_pages
+  mount_pages(browse_bp, "market", names=["market-home"])
 
   @browse_bp.get("/all/")
   @cache_page(tag="browse")