fix(auth): fail closed when the adminAuth roles join errors (stable) (#975)

Closes #968 on stable. Backport of #974.

The roles-join fallback in adminAuth fabricated role_name='super_admin' on ANY database error, so a transient fault silently granted super_admin for its duration. Gate it on isMissingRolesSchema(), moved to utils/dbErrors.js and shared with apiTokenAuth, with the predicate tightened to trust SQLSTATE 42P01/42703 on Postgres and exact driver phrasing on SQLite.

backend/__tests__/middleware/apiTokenRoleFallback.test.js

@@ -29,4 +29,44 @@ describe('apiTokenAuth roles-schema fallback predicate (GHSA-9697)', () => {
   it('rejects a missing-table error for an unrelated table', () => {
     expect(isMissingRolesSchema(new Error('SQLITE_ERROR: no such table: api_tokens'))).toBe(false);
   });
+
+  // knex prefixes the failing SQL to err.message, and that SQL always names
+  // `roles` on this join — so the message substring proves nothing about the
+  // error, and only an exact driver phrase (or a SQLSTATE) may be trusted.
+  // These are real knex message shapes, captured from the actual query.
+  describe('with knex\'s SQL prefix on the message (#968)', () => {
+    const withSql = (driverMessage) => new Error(
+      'select `roles`.`name` as `role_name` from `admin_users` '
+      + 'left join `roles` on `roles`.`id` = `admin_users`.`role_id` '
+      + `where \`admin_users\`.\`id\` = 1 limit 1 - ${driverMessage}`,
+    );
+
+    it('accepts both legitimate upgrade-window states', () => {
+      // pre-054: the roles table does not exist yet
+      expect(isMissingRolesSchema(
+        Object.assign(withSql('SQLITE_ERROR: no such table: roles'), { code: 'SQLITE_ERROR' }),
+      )).toBe(true);
+      // post-054, pre-057: roles exists, admin_users.role_id not added yet
+      expect(isMissingRolesSchema(
+        Object.assign(withSql('SQLITE_ERROR: no such column: admin_users.role_id'), { code: 'SQLITE_ERROR' }),
+      )).toBe(true);
+    });
+
+    it('rejects an unrelated "does not exist" fault despite the SQL naming roles', () => {
+      // pgbouncer transaction pooling loses a named prepared statement
+      // (SQLSTATE 26000). Transient — the fallback query would succeed on a
+      // fresh connection, so accepting this would fabricate super_admin.
+      expect(isMissingRolesSchema(
+        Object.assign(withSql('prepared statement "S_1" does not exist'), { code: '26000' }),
+      )).toBe(false);
+      // The DB role/user, not the roles table.
+      expect(isMissingRolesSchema(
+        Object.assign(withSql('role "picpeak" does not exist'), { code: '28000' }),
+      )).toBe(false);
+      expect(isMissingRolesSchema(
+        Object.assign(withSql('database "picpeak" does not exist'), { code: '3D000' }),
+      )).toBe(false);
+      expect(isMissingRolesSchema(withSql('Connection terminated unexpectedly'))).toBe(false);
+    });
+  });
 });