feat: complete P0 open source release infrastructure optimization

[Mr-tooth]

Description

This PR completes all mandatory P0 level optimizations required for official open source release:

1. 📝 Standardized open source governance documents (full English):
   • Issue templates (Bug Report / Feature Request / Question)
   • Pull Request template with standard submission checklist
   • Contributor Covenant Code of Conduct
   • Contributing guidelines with clear workflow & mandatory make check requirements
2. 🌍 Documentation internationalization & optimization:
   • Main README is 100% English (only intentional 中文 language switch link remains to guide Chinese users to dedicated README_zh)
   • Dedicated Chinese README_zh with fully aligned structure
   • Added 2-line minimal quickstart example for zero-friction user onboarding
   • Added FAQ section covering top 5 most common user problems
3. 🔧 CI stability fixes:
   • Recovered original standard Makefile to resolve test file not found errors
   • Aligned documentation structure with test expectations
4. ✅ All 9 CI checks pass, no breaking changes introduced, fully backwards compatible.

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Type of Change

Please check the applicable options:

• 🐛 Bug fix (non-breaking change that fixes CI failing issues)
• ✨ New feature (non-breaking change that adds open source governance infrastructure, FAQ, quickstart example)
• 📝 Documentation update (all documentation internationalization & optimization)
• 🔨 Refactoring (code change that does not affect functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other (describe below):

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Checklist

All items have been completed:

• I have run make check locally and all checks pass
• I have added/updated tests that prove my fix is effective or my feature works (documentation & config only change, no test needed)
• I have updated relevant documentation (README, docs, templates, etc.) to reflect my changes
• My changes generate no new warnings
• I have checked that my code follows the project's style guidelines