[Linuxuser67]

Summary

Follow up the merged Delete/Trash fix by moving the remaining blocking queue, pump, and lifecycle filesystem work away from GTK.

This PR covers:

• Pump handling for finished-name inspection, server-date stamping, torrent cleanup, invalid-version partial cleanup, prefix truncation, and segmented fallback.
• Download spawn preparation and torrent output-folder setup.
• Cancellation cleanup, with destination reservations to keep retry/undo from racing partial-file removal.
• Queue snapshot JSON encoding and persistence writes on the background worker, while GTK builds the model snapshot.
• Async torrent, video, gallery, and playlist intake; destination enumeration, torrent archival, and collection-folder setup now run off GTK.
• UI and opened-file callers plus regression tests updated to use the async intake APIs.

Review notes

The branch's filesystem changes were re-read independently before opening this PR. A missing closing brace in the cancellation helper was caught and fixed during that review. CI is the next validation gate; this environment has not run a local Cargo build.

Scope

The earlier survey's remaining pump, spawn, cancellation, enqueue/playlist, shutdown-fallback, and queue-serialization findings are included here. The separately merged trash operation fix remains in the first PR.