Fix stale cache-header assertion in test_server

'select *' is invalid SQL, so /api/query returns 200 with success=false.
The test asserted that error response got max-age=3600, which stopped
being true once we stopped caching errors. Assert both cases instead:
a valid query is cached, a failed one isn't.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: akariv

tests/test_server.py

@@ -29,10 +29,16 @@ def test_server_init():
     assert resp.status_code == 403
     assert resp.headers.get('Cache-Control') == 'no-cache'
 
-    resp = client.get('/api/query?query=select *')
+    resp = client.get('/api/query?query=select 1 as x')
     assert resp.status_code == 200
     assert resp.headers['Cache-Control'] == 'max-age=3600'
 
+    # A failed query is reported as a 200 with success=false - it must not be cached
+    resp = client.get('/api/query?query=select *')
+    assert resp.status_code == 200
+    assert resp.get_json()['success'] is False
+    assert resp.headers['Cache-Control'] == 'no-cache'
+
     resp = client.get('/wait/1')
     assert resp.status_code == 200