fix: restore green builds and align frontend-backend contracts (P0)

- Isolate Settings tests from .env and process env leakage
- Fix analytics metadata test to unwrap psycopg Json wrapper
- Remove unused state variables causing frontend build failures
- Fix ReviewPage to use /classifications endpoint instead of nonexistent /result
- Normalize ReviewPage status enums (failed not error) and access_type values
- Align api.ts types with backend response shapes (ReplayPage, AnalyticsData, AgentUsage)

backend/tests/unit/analytics/test_event_recorder.py

@@ -145,4 +145,11 @@ class TestPostgresAnalyticsRecorder:
         )
         call_args = mock_conn.execute.call_args
         params = call_args[0][1]
-        assert params["metadata"] == {"key": "val"}
+        # PostgresAnalyticsRecorder wraps metadata with psycopg Json() adapter.
+        # Unwrap to compare the inner dict.
+        from psycopg.types.json import Json
+
+        meta = params["metadata"]
+        if isinstance(meta, Json):
+            meta = meta.obj
+        assert meta == {"key": "val"}