fix/imports

[gabrielecalafange]

Implemented cleanup that marks stale imports as failed when they exceed the RabbitMQ message timeout, preventing endless in_progress loops and stale scheduled tasks. The scheduler now expires stuck imports before deciding whether to enqueue new ones, using the queue expiration setting as the cutoff, and records a clear timeout reason.

• Updated report_import.py to add IMPORT_TIMEOUT_REASON, expire overdue scheduled/in_progress imports using the queue TTL, log the event, and reuse the same settings inside check_unprocessed_imports.
• Added test_mark_stale_import_failed in test_schedule_imports.py to verify timed-out imports are flipped to failed with the proper reason and a fresh import is scheduled.

[marianezei]

lgtm