Fix stale TV listings after deleting files and restarting VuIO

[vyrti]

TVs can retain deleted files even after VuIO restarts: the HTTP listener serves the cached library while startup scanning runs, but completing that scan did not invalidate Browse responses or publish a ContentDirectory change. The revision also restarted at 1 every time.

Seed the revision per boot and publish a change after startup media and playlist scanning. This clears responses cached before cleanup and tells subscribed TVs to refresh. Startup regression coverage exercises both scan_on_startup settings.

Also handle missing paths in generic watcher events and run missing-file reconciliation every five minutes independently of full discovery, including when full rescans are disabled. Preserve the live cleanup setting, offline-library grace, unreadable files, and HTTP(S) radio streams. Regression coverage includes deleted folders, Browse totals and revisions, disabled cleanup, radio URLs, and permission failures.

Missing-file recovery now probes indexed paths every five minutes. It uses paged fingerprints and performs existence checks; full directory walks and metadata parsing retain their existing cadence.

Validation:

• Default-feature core unit tests and Samsung Browse, UPnP eventing, path-normalization, and regression integration suites: 685 passed, 1 existing ignored test.
• Core unit tests without default features: 407 passed.
• CI formatting command and git diff --check passed.
• CI Clippy command across the four shipping crates, all targets and all features, with warnings denied.