Support for videos on private sites

Checklist

• This feature I'm requesting is already implemented in yt-dlp.
• This feature is merely a UI/UX update.
• This feature is suitable for primary users with little knowledge about yt-dlp.
• This feature is available for most websites, not only the video platform I use.
• This feature is suitable for a large variety of videos.
• This feature is not going to conflict with many of the existing options.

Is your feature request related to a problem? Please describe.

Currently, Seal only appears to allow downloading videos from public sites. It has no good support for --username / --password flags or the --netrc flag (this is possible using custom commands but then that disables most of the other features).

This makes downloading from private sites, like Nebula, a bit tedious.

Describe the solution you'd like

1. Provide a large textarea in settings where user can enter their .netrc entries.
2. Save that textbox as a text file on phone's disk, where it is accessible by the yt-dlp
3. Pass path to that text file via --netrc flag, when calling yt-dlp

Video link

No response

Additional context

https://github.com/yt-dlp/yt-dlp?tab=readme-ov-file#authentication-with-netrc

No source file or test is named. Start by locating the settings screen and the code that invokes yt-dlp, then trace how settings are persisted on the phone. Done means users can enter .netrc entries, the text is saved as a file, and yt-dlp receives its path through --netrc without losing existing features.