SX docs: configurable shell, SX-native event handlers, nav fixes

- Configurable page shell (~sx-page-shell kwargs + SX_SHELL app config)
  so each app controls its own assets — sx docs loads only sx-browser.js
- SX-evaluated sx-on:* handlers (eval-expr instead of new Function)
  with DOM primitives registered in PRIMITIVES table
- data-init boot mode for pure SX initialization scripts
- Jiggle animation on links while fetching
- Nav: 3-column grid for centered alignment, is-leaf sizing,
  fix map-indexed param order (index, item), guard mod-by-zero
- Async route eval failure now falls back to server fetch
  instead of silently rendering nothing
- Remove duplicate h1 title from ~doc-page
- Re-bootstrap sx-ref.js + sx-browser.js

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

shared/infrastructure/factory.py

@@ -302,9 +302,10 @@ def create_base_app(
                         return
                 return redirect(f"/auth/login?prompt=none&next={_quote(request.url, safe='')}")
 
-    @app.before_request
-    async def _load_user():
-        await load_current_user()
+    if not no_db:
+        @app.before_request
+        async def _load_user():
+            await load_current_user()
 
     # Register any app-specific before-request hooks (e.g. cart loader)
     if before_request_fns: