Add PolinRider malware guard workflow

[khushalVekariya]

Task

• Adds .github/workflows/polinrider-guard.yml — a CI workflow that runs on every push and pull request
• Scans tracked files for known PolinRider malware indicators (file paths, string markers, asset payloads)
• Checks font, image, and SVG assets for embedded JS/shell payloads
• Detects suspicious Git propagation behaviour in .sh, .bat, .cmd, and .ps1 scripts
• Fails the build immediately on any match, blocking the merge

[Copilot]

Pull request overview

This PR adds a dedicated GitHub Actions workflow to detect and block known PolinRider malware indicators during CI, preventing merges when suspicious files/strings/assets or Git-propagation behaviors are detected.

Changes:

• Added a new workflow that runs on push, pull_request, and workflow_dispatch.
• Implemented scans for known indicator paths/strings across tracked files via git ls-files and git grep.
• Added binary-asset checks (fonts/images/SVG) and script-behavior checks for suspicious Git propagation patterns.

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