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>

blog/bp/admin/routes.py

@@ -27,33 +27,22 @@ def register(url_prefix):
         "base_title": f"{config()['title']} settings",
       }
 
-    @bp.get("/")
-    @require_admin
-    async def home():
-      from shared.sx.page import get_template_context
-      from sx.sx_components import render_settings_page, render_settings_oob
+    @bp.before_request
+    async def _prepare_page_data():
+        ep = request.endpoint or ""
+        if "defpage_settings_home" in ep:
+            from shared.sx.page import get_template_context
+            from sx.sx_components import _settings_main_panel_sx
+            tctx = await get_template_context()
+            g.settings_content = _settings_main_panel_sx(tctx)
+        elif "defpage_cache_page" in ep:
+            from shared.sx.page import get_template_context
+            from sx.sx_components import _cache_main_panel_sx
+            tctx = await get_template_context()
+            g.cache_content = _cache_main_panel_sx(tctx)
 
-      tctx = await get_template_context()
-      if not is_htmx_request():
-          html = await render_settings_page(tctx)
-          return await make_response(html)
-      else:
-          sx_src = await render_settings_oob(tctx)
-          return sx_response(sx_src)
-
-    @bp.get("/cache/")
-    @require_admin
-    async def cache():
-        from shared.sx.page import get_template_context
-        from sx.sx_components import render_cache_page, render_cache_oob
-
-        tctx = await get_template_context()
-        if not is_htmx_request():
-            html = await render_cache_page(tctx)
-            return await make_response(html)
-        else:
-            sx_src = await render_cache_oob(tctx)
-            return sx_response(sx_src)
+    from shared.sx.pages import mount_pages
+    mount_pages(bp, "blog", names=["settings-home", "cache-page"])
 
     @bp.post("/cache_clear/")
     @require_admin
@@ -65,7 +54,7 @@ def register(url_prefix):
             html = render_comp("cache-cleared", time_str=now.strftime("%H:%M:%S"))
             return sx_response(html)
 
-        return redirect(url_for("settings.cache"))
+        return redirect(url_for("settings.defpage_cache_page"))
     return bp