Improve remote video playback reliability and VLC lifecycle handling

[marinofaggiana]

Summary

Improve remote video playback reliability and prevent VLC lifecycle races when changing or closing videos.

Changes

• Replace the AVFoundation status observation with an async playability check.
• Fall back to VLC when the AVFoundation probe fails or exceeds 8 seconds.
• Cancel obsolete playback probes when the selected video changes.
• Wait for VLC to stop completely before detaching its drawable, dismissing the player, or changing video.
• Recover the SwiftUI playback state when VLC presentation is rejected, allowing a new playback attempt.
• Forward the configured user agent to remote playback.
• Add privacy-safe VLC diagnostics for presentation, playback requests, and state changes. Direct URL paths, queries, and tokens are never logged.
• Update the app version to 34.1.1.

Motivation

Remote videos could remain indefinitely in the loading state when the AVFoundation probe did not complete or when a VLC presentation request was rejected during a transition.

VLC could also continue accessing its rendering view while the player was being dismissed or another video was selected, potentially triggering an Auto Layout operation outside the main thread.

Testing

• Nextcloud scheme builds successfully in Xcode.
• Verified cancellation and fallback paths compile correctly.
• Verified VLC shutdown completes before the drawable and controller are released.
• Verified rejected presentations reset the playback state and can be retried.

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI

[marinofaggiana]

#4209