Vibecondom security check

[ngmisl]

ci: Add automated security scanning workflow by vibecondom

Vibecondom: A security tool for detecting hidden characters and malicious prompt injections in text content intended for LLMs. Scans for control characters, zero-width characters, Unicode tag characters, bidirectional text manipulations, mixed scripts, and encoded content. Built with Go 1.24 focusing on security and type safety.

This commit introduces a GitHub Actions workflow (security-scan.yaml)
to enhance repository security by performing automated checks on each
push and pull request to the main branch.

The workflow includes the following key security scans:

1. Vibecondom Scan:
   • Builds the Vibecondom tool from source.
   • Runs Vibecondom against the repository to detect:
     • Hidden or malicious Unicode characters.
     • ASCII control characters.
     • Suspicious Base64 encoded strings, with deep inspection
       enabled via the -decode-base64 flag.

This proactive scanning pipeline aims to identify and flag potential
security risks and undesirable content early in the development lifecycle,
contributing to a more secure codebase.