Fetch nav-tree fragment from blog, drop local menu_items query

Navigation is now rendered by blog as an HTML fragment. This app
fetches it with its own app_name and path for correct highlighting.

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

app.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 import path_setup  # noqa: F401  # adds shared/ to sys.path
 from pathlib import Path
 
-from quart import g
+from quart import g, request
 from jinja2 import FileSystemLoader, ChoiceLoader
 
 from shared.infrastructure.factory import create_base_app
@@ -14,12 +14,15 @@ from bp import register_account_bp, register_auth_bp, register_fragments
 async def account_context() -> dict:
     """Account app context processor."""
     from shared.infrastructure.context import base_context
-    from shared.services.navigation import get_navigation_tree
     from shared.infrastructure.cart_identity import current_cart_identity
+    from shared.infrastructure.fragments import fetch_fragment
 
     ctx = await base_context()
 
-    ctx["menu_items"] = await get_navigation_tree(g.s)
+    ctx["nav_tree_html"] = await fetch_fragment(
+        "blog", "nav-tree",
+        params={"app_name": "account", "path": request.path},
+    )
 
     # Cart data (consistent with all other apps)
     ident = current_cart_identity()