docs: Add comprehensive CONTRIBUTING.md guide

[AlexGromer]

Summary

Added comprehensive contribution guidelines in both English and Russian to help new contributors get started with the project.

Changes

• ✅ Added CONTRIBUTING.md with bilingual documentation
• ✅ Development setup instructions
• ✅ Testing guidelines with examples (Bash + Go)
• ✅ Pull Request process and commit message format
• ✅ Coding standards (following Google Shell Style Guide + Effective Go)
• ✅ Security guidelines
• ✅ Pre-submission checklist

Why This Matters

This will help potential contributors:

• Understand how to set up their development environment
• Write tests that match the project's standards
• Follow the established commit message format
• Understand security requirements
• Navigate the PR process smoothly

Test Plan

• Documentation reviewed
• Both English and Russian sections complete
• Examples tested and verified
• Links to project files validated

Related

Part of initial repository setup to ensure a welcoming and well-documented contribution process.

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🤖 Generated with Claude Code

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