Unify runtime state in SQLite and add rollout observability

tests/test_web_observability.py

@@ -0,0 +1,37 @@
+
+from fastapi.testclient import TestClient
+
+from web.app import app
+
+
+client = TestClient(app)
+
+
+def test_healthz_returns_ok_shape():
+    response = client.get('/healthz')
+    assert response.status_code == 200
+    payload = response.json()
+    assert payload['status'] in {'ok', 'degraded'}
+    assert 'db' in payload
+    assert 'state_storage_mode' in payload
+    assert 'cities_count' in payload
+
+
+def test_system_status_returns_summary_shape():
+    response = client.get('/api/system/status')
+    assert response.status_code == 200
+    payload = response.json()
+    assert 'db' in payload
+    assert 'features' in payload
+    assert 'integrations' in payload
+    assert 'cache' in payload
+    assert 'probability' in payload
+    assert 'rollout' in payload['probability']
+    assert payload['probability']['rollout']['decision']['decision'] in {'hold', 'observe', 'promote'}
+    assert 'cities_count' in payload
+
+
+def test_metrics_endpoint_returns_prometheus_payload():
+    response = client.get('/metrics')
+    assert response.status_code == 200
+    assert 'polyweather_http_requests_total' in response.text