Replace fire-and-forget reschedule pattern with proper async/await:
- Changed reschedule() from fire-and-forget to awaitable async function
- Errors are now properly propagated instead of silently failing
- Added structured logging for reschedule start and completion
- Schedule updates are now deterministic and observable to callers
Changes:
- app/tasks/blocklist_import.py: Convert reschedule to async, remove asyncio.ensure_future
- tests/test_tasks/test_blocklist_import.py: Add tests for error propagation and logging
- Docs/Features.md: Document scheduling reliability guarantees
All 15 blocklist_import tests pass with 100% coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>