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

@@ -19,6 +19,7 @@ async def events_context() -> dict:
     - cart_count/cart_total: via cart service (shared DB)
     """
     from shared.infrastructure.context import base_context
+    from shared.services.navigation import get_navigation_tree
     from shared.services.registry import services
     from shared.infrastructure.cart_identity import current_cart_identity
     from shared.infrastructure.fragments import fetch_fragment
@@ -29,6 +30,8 @@ async def events_context() -> dict:
         "blog", "nav-tree",
         params={"app_name": "events", "path": request.path},
     )
+    # Fallback for _nav.html when nav-tree fragment fetch fails
+    ctx["menu_items"] = await get_navigation_tree(g.s)
 
     # Cart data via service (replaces cross-app HTTP API)
     ident = current_cart_identity()