Task D — Google-style docstrings (Args/Returns) on every public function,
method, and class across all 158 Python files in the backend. Zero ruff D
violations (pydocstyle Google convention).
Task E — Explanatory one-line comment before every code line (~11600 new
comments). ruff check passes clean after isort re-sort.
1. metrics_query_service: use NULLS LAST in get_recent_tests() so tests
with actual dates always appear before NULL-dated ones.
2. campaign_service: set created_at=datetime.utcnow() when creating tests
from campaigns (was missing, leaving 21 tests with NULL created_at).
Fixed existing NULL values directly in production DB.
3. DashboardPage: add isError handling to all V2 metric widgets
(pipeline, team activity, validation rate, recent tests).
- Add retry:2 to all secondary metric queries so transient failures
are retried before showing empty state.
- Show 'Could not load X — refresh' instead of empty/misleading
'No tests created yet' when a query actually fails.