feat(111): findings workflow + SLA settings (#135)
Implements spec 111 (Findings workflow + SLA) and fixes Workspace findings SLA settings UX/validation.
Key changes:
- Findings workflow service + SLA policy and alerting.
- Workspace settings: allow partial SLA overrides without auto-filling unset severities in the UI; effective values still resolve via defaults.
- New migrations, jobs, command, UI/resource updates, and comprehensive test coverage.
Tests:
- `vendor/bin/sail artisan test --compact` (1779 passed, 8 skipped).
Co-authored-by: Ahmed Darrazi <ahmed.darrazi@live.de>
Reviewed-on: #135