[markusbrand]

Description

This PR fixes runtime crashes caused by comparisons between offset-naive and offset-aware datetimes in backend telemetry logging, retention pruning, and the doctor CLI, as well as fixing a time-bomb test failure in test_telemetry_api_routes.

Key Changes

1. Telemetry Pruning & Logging (backend/app/telemetry/service.py):

   • Explicitly supply created_at=datetime.now(timezone.utc) when instantiating ServerEvent in log_server_event rather than relying solely on SQLite's server-side naive default in Python memory.
   • Configure bulk deletion queries in prune_telemetry_records with .execution_options(synchronize_session=False) to avoid evaluating SQL deletion predicates in Python memory against session entities with disparate datetime representations.
   • Normalize naive timestamps to timezone-aware UTC in ingest_telemetry_batch and upsert_client_ping.

2. Doctor CLI Timeline Sorting (backend/app/cli/doctor.py):

   • Added _normalize_timeline_ts to safely normalize timestamps to UTC prior to comparison in show_trace and generate_llm_prompt timelines.

3. Test Suite & OpenSpec Artifacts:

   • Updated backend/tests/test_telemetry.py to use dynamic relative UTC timestamps so test summaries are not immediately purged by 30-day retention policies.
   • Added regression test cases for log_server_event pruning, naive datetime ingestion, and mixed-timestamp timeline sorting.
   • Created OpenSpec change artifacts in openspec/changes/fix-telemetry-datetime-timezone-handling/.

Verification

• Full QA suite passed (./scripts/run-qa.sh):
  • client-tauri: 21 passed, 0 failed.
  • web: build passed.
  • backend: 111 passed, 0 failed.
  • docs: mkdocs build passed.