Show settings cog on root header for admin users

Pass settings_url and is_admin to header-row component so the blog
settings cog appears on the root header row for admin users across
all services. Links to blog /admin/.

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

shared/sexp/helpers.py

@@ -33,6 +33,9 @@ def get_asset_url(ctx: dict) -> str:
 
 def root_header_html(ctx: dict, *, oob: bool = False) -> str:
     """Build the root header row HTML."""
+    rights = ctx.get("rights") or {}
+    is_admin = rights.get("admin") if isinstance(rights, dict) else getattr(rights, "admin", False)
+    settings_url = call_url(ctx, "blog_url", "/admin/") if is_admin else ""
     return render(
         "header-row",
         cart_mini_html=ctx.get("cart_mini_html", ""),
@@ -42,6 +45,8 @@ def root_header_html(ctx: dict, *, oob: bool = False) -> str:
         nav_tree_html=ctx.get("nav_tree_html", ""),
         auth_menu_html=ctx.get("auth_menu_html", ""),
         nav_panel_html=ctx.get("nav_panel_html", ""),
+        settings_url=settings_url,
+        is_admin=is_admin,
         oob=oob,
     )