fix(video): align visible playback and time controls

[kcng0]

Updates video interactions across Visible and shared players:

• expose Delete directly in Visible selection
• exit video playback on the first system Back
• navigate previous/next videos in the Visible folder
• show current/total time in VLC-style format during playback and seeking

Verification:

• flutter analyze
• video player control tests
• player/viewer Back tests
• Visible grid and playlist tests
• git diff --check

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