Use Weverse preview endpoint if no auth provided

[seproDev]

IMPORTANT: PRs without the template will be CLOSED

Description of your pull request and other information

Change Weverse extractor to try and download videos using the preview endpoint if no credentials are provided.

Template

Before submitting a pull request make sure you have:

• At least skimmed through contributing guidelines including yt-dlp coding conventions
• Searched the bugtracker for similar pull requests
• Checked the code with flake8 and ran relevant tests

In order to be accepted and merged into yt-dlp each piece of code must be in public domain or released under Unlicense. Check all of the following options that apply:

• I am the original author of this code and I am willing to release it under Unlicense
• I am not the original author of this code but it is in public domain or released under Unlicense (provide reliable evidence)

What is the purpose of your pull request?

• Fix or improvement to an extractor (Make sure to add/update tests)
• New extractor (Piracy websites will not be accepted)
• Core bug fix/improvement
• New feature (It is strongly recommended to open an issue first)

Copilot Summary

🤖 Generated by Copilot at 302a6c7

Summary

🔒🌐🛠️

Refactor weverse extractor to improve authentication and access handling, and add preview support.

The weverse extractor was due
For a refactor to make it more true
To the access rights logic
And the endpoints biologic
That provide previews for me and for you

Walkthrough

• Move token check and login error to _call_api and _call_post_api functions (link)
• Use alternative endpoints for previews without authentication or access rights (link)