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.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
