fix(account): close deletion cache gap

Require authenticated sidecar cache purge before a deletion can complete and keep failures retryable. Mount tombstones outside restored application data while leaving deletion disabled by default.

tools/summarizer/tests/test_app.py

@@ -510,6 +510,22 @@ def test_health_stays_open_so_probes_and_healthchecks_work(monkeypatch):
     assert client.get("/health").status_code == 200
 
 
+def test_cache_purge_requires_service_token_and_clears_content(monkeypatch):
+    module = load_app_module(monkeypatch, service_token="s3cret")
+    module.cache["synthetic-key"] = "synthetic-summary"
+    client = TestClient(module.app)
+
+    assert client.delete("/maintenance/cache").status_code == 401
+    response = client.delete(
+        "/maintenance/cache",
+        headers={"X-Ai-Service-Token": "s3cret"},
+    )
+
+    assert response.status_code == 200
+    assert response.json() == {"cleared": 1}
+    assert len(module.cache) == 0
+
+
 def test_endpoints_stay_open_when_no_token_is_configured(monkeypatch):
     module = load_app_module(monkeypatch)
     client = TestClient(module.app)