Store original video metadata before normalization

[Fuitad]

When a movie is uploaded, zou normalizes it to the project's target resolution, then saves the normalized dimensions to the database. This means we lose track of what the user actually uploaded.

Now we grab the original width, height, duration and file size from the uploaded file and stash them in the preview_file.data JSONB column before normalization runs. No migration needed since the column already exists.

Also added the data field to the playlist entity preview-files API response so the frontend can access it.

Problem
We needed a way to access the size of the original file uploaded. Right now, what is saved in the database in terms of height and width is only what zou re-encodes.

Solution
The original data is saved in the data column of the preview_file table. All existing stuff, no migration, no issue for previous uploads :).

[nledez]

Thank you for your contribution @Fuitad. We'll review this as soon as possible.

[Fuitad]

Hello @nledez. Just wondering if there's any interest in merging this into the main zou branch. If not (which is fine), we'll start our own branch to be able to incorporate it. Thanks!