Add User-Agent rotation system (#198)

[ssiweifnag]

Summary

This PR implements a User-Agent rotation system to reduce fingerprinting when scanning, as requested in issue #198.

Changes

1. Added get_random_user_agent() in user_scanner/core/helpers.py

A new function that returns a random User-Agent string from a curated list of 18 modern user agents:

• PC (Windows): Chrome, Firefox, Edge
• PC (macOS): Chrome, Firefox, Safari
• Mobile: iPhone 15 (Safari), Pixel 8 (Chrome), Samsung Internet
• Version: Updated 2026-02 for current browser versions

2. Updated substack.py as Demo

The substack.py module now uses get_random_user_agent() instead of hardcoded User-Agent.

Remaining Modules

The following modules still use hardcoded User-Agents and can be updated similarly:

• user_scan/creator/hashnode.py
• user_scan/creator/medium.py
• user_scan/creator/producthunt.py
• user_scan/creator/twitch.py
• user_scan/gaming/chess_com.py
• user_scan/gaming/monkeytype.py
• user_scan/gaming/battlenet.py
• user_scan/social/youtube.py
• user_scan/social/x.py

Issue Reference

#198

[kaifcodec]

@ssiweifnag Appreciate you efforts but I'm going to close this PR for now. While the get_random_user_agent() function works, the implementation needs to be applied to all existing modules simultaneously to meet the issue requirements.

Re-fork the latest main, implement the logic globally across all modules, and submit a new PR with a clean, single commit. This will keep the project history organized. Looking forward to the updated version!

[kaifcodec]

@ssiweifnag One final note: your Git identity is currently set to ＰＣ <pc@PCdeMac-mini.lan>.

Since that's a local email, GitHub can't link these commits to your account, so you won't show up in the Contributors list. If you want credit for the work, make sure to set your global user.name and user.email correctly if you plan to open a PR next.