Restore menu_items fallback for nav, update shared submodule

Keep get_navigation_tree() as fallback when nav-tree fragment fetch
fails. Update shared submodule with fixed app slug URLs in nav.

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

app.py

@@ -51,6 +51,7 @@ async def cart_context() -> dict:
     Global cart_count / cart_total stay global for cart-mini.
     """
     from shared.infrastructure.context import base_context
+    from shared.services.navigation import get_navigation_tree
     from shared.infrastructure.fragments import fetch_fragment
 
     ctx = await base_context()
@@ -59,6 +60,8 @@ async def cart_context() -> dict:
         "blog", "nav-tree",
         params={"app_name": "cart", "path": request.path},
     )
+    # Fallback for _nav.html when nav-tree fragment fetch fails
+    ctx["menu_items"] = await get_navigation_tree(g.s)
 
     # Cart app owns cart data — use g.cart from _load_cart
     all_cart = getattr(g, "cart", None) or []