Update technical-notes-codex.md with Cove integration and recent changes
- Add complete Cove Data Protection integration section: API details,
column codes, status mapping, inbox flow, CoveAccount model, routes,
migrations, background thread, settings UI
- Update Data Model section: CoveAccount model, Job.cove_account_id,
JobRun.source_type + external_id, SystemSettings Cove fields
- Update Application Architecture: cove_importer_service background thread
- Add debug logging snippet for ticket linking issues
- Add Recent Changes entry for 2026-02-23
- Add Cove files to Quick References
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>