Add SOCKS proxy support

[vasiliadi]

Summary

Adds SOCKS proxy support for generic proxy configuration and the CLI.

Changes

• Enables the requests[socks] extra so PySocks is installed transitively.
• Adds socks_url to GenericProxyConfig and uses it as the fallback proxy for HTTP and HTTPS requests.
• Adds a --socks-proxy CLI argument that passes SOCKS proxy URLs into GenericProxyConfig.
• Covers SOCKS-only and mixed proxy fallback behavior in proxy and CLI tests.

[coveralls]

Coverage Report for CI Build 26670183465

Coverage remained the same at 100.0%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	507
Covered Lines:	507
Line Coverage:	100.0%
Coverage Strength:	7.0 hits per line

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💛 - Coveralls

[vasiliadi]

Or maybe it’s better to edit README.md

-Alternatively to using [Webshare](https://github.com/jdepoix/youtube-transcript-api#using-webshare), you can set up any generic HTTP/HTTPS/SOCKS proxy using the GenericProxyConfig class:
+Alternatively to using [Webshare](https://github.com/jdepoix/youtube-transcript-api#using-webshare), you can set up any generic HTTP/HTTPS proxy using the GenericProxyConfig class:

[vasiliadi]

And my ruff format youtube_transcript_api doesn't find any issues: 15 files left unchanged.
I use ruff==0.15.15. So have no idea how to fix static-checks.

Poe => ruff format youtube_transcript_api --check
Would reformat: youtube_transcript_api/test/test_cli.py
1 file would be reformatted, 14 files already formatted
Error: Process completed with exit code 1.