refactor(admin): embed roles data in user list query and update role display

- remove separate `/zen/api/roles` fetch and `roleColorMap` state from UsersPage
- update SQL query to include aggregated roles array per user via subquery
- replace single role badge with multi-badge display supporting overflow indicator

src/features/auth/api.js

@@ -129,7 +129,15 @@ async function handleListUsers(request) {
   const quotedSortColumn = `"${sortColumn}"`;
 
   const result = await query(
-    `SELECT id, email, name, role, image, email_verified, created_at FROM zen_auth_users ORDER BY ${quotedSortColumn} ${order} LIMIT $1 OFFSET $2`,
+    `SELECT u.id, u.email, u.name, u.role, u.image, u.email_verified, u.created_at,
+      COALESCE(
+        (SELECT json_agg(json_build_object('id', r.id, 'name', r.name, 'color', r.color) ORDER BY r.created_at ASC)
+         FROM zen_auth_roles r
+         JOIN zen_auth_user_roles ur ON ur.role_id = r.id
+         WHERE ur.user_id = u.id),
+        '[]'::json
+      ) AS roles
+     FROM zen_auth_users u ORDER BY u.${quotedSortColumn} ${order} LIMIT $1 OFFSET $2`,
     [limit, offset]
   );