fix: reset Video record after orphan cleanup

[dreamcreated]

Problem

Fixes #17

check_and_delete_orphan in app/services/storage.py correctly removes the physical media, preview, and thumbnail files from disk when a video has no remaining active UserVideoRef associations. However, the Video record itself is never updated — status stays "COMPLETE" and file_path still points to the deleted file.

Impact:

• A new user subscribing to the same channel later will get a new UserVideoRef, but attempting to stream the video returns a 404 ("Video file missing from disk")
• Auto-download logic skips the video because status == "COMPLETE", so it never re-downloads
• Users have no direct path to recover the video without manual DB intervention

Fix

After deleting all files from disk, reset the Video record to reflect its actual state:

video.status = "CATALOGED"
video.file_path = None
video.file_size_bytes = 0
await db.commit()

This makes the video eligible for re-download if a new user subscribes to the channel.

Changes

• app/services/storage.py: Reset video.status, video.file_path, and video.file_size_bytes after orphan deletion; moved db.commit() inside the function (was missing entirely).