Fix: use already-loaded user data for admin check instead of redundant DB query

fix-admin-check.patch

diff --git a/backend/src/routes/auth.ts b/backend/src/routes/auth.ts
index 2aef333..51bdb83 100644
--- a/backend/src/routes/auth.ts
+++ b/backend/src/routes/auth.ts
@@ -369,17 +369,8 @@ router.post(
 router.get('/user', authenticate, async (req, res) => {
   const authReq = req as unknown as AuthenticatedRequest;
 
-  // Check if user is a platform admin
-  let is_platform_admin = false;
-  try {
-    const adminCheck = await query(
-      'SELECT is_system_admin FROM users WHERE id = $1',
-      [authReq.user!.id]
-    );
-    is_platform_admin = adminCheck.rows[0]?.is_system_admin === true;
-  } catch {
-    // Column may not exist yet
-  }
+  // Check if user is a platform admin (already loaded by authenticate middleware)
+  const is_platform_admin = (authReq.user as any)?.is_system_admin === true;
 
   // Load org context if user has an organization
   let organization = null;