docs: Add comprehensive open source project improvements

- Add essential open source files (CONTRIBUTING.md, CODE_OF_CONDUCT.md, SECURITY.md, CHANGELOG.md, CONTRIBUTORS.md)
- Add GitHub issue and PR templates
- Add CI/CD workflows (CI, docs, release, dependabot)
- Add pre-commit hooks configuration
- Add documentation enhancements (architecture, governance, contributing, community)
- Add developer experience scripts (setup-dev, run-tests, format-code, check-code)
- Add community features (SUPPORT.md, .all-contributorsrc)
- Enhance README badges and project metadata
- Update mkdocs.yml navigation structure

SECURITY.md

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+# Security Policy
+
+## Supported Versions
+
+We actively support the following versions of Semantica with security updates:
+
+| Version | Supported          |
+| ------- | ------------------ |
+| 0.0.1   | :white_check_mark: |
+| < 0.0.1 | :x:                |
+
+## Reporting a Vulnerability
+
+We take security vulnerabilities seriously. If you discover a security vulnerability, please follow these steps:
+
+### 1. **Do NOT** create a public GitHub issue
+
+Security vulnerabilities should be reported privately to prevent potential exploitation.
+
+### 2. Email Security Team
+
+Send an email to: **semantica-dev@users.noreply.github.com**
+
+Include the following information:
+
+- **Type of vulnerability** (e.g., XSS, SQL injection, authentication bypass)
+- **Affected component** (module, function, or file)
+- **Steps to reproduce** (detailed description or proof-of-concept code)
+- **Potential impact** (what could an attacker do?)
+- **Suggested fix** (if you have one)
+- **Your contact information** (for follow-up questions)
+
+### 3. Response Timeline
+
+- **Initial Response**: Within 48 hours
+- **Status Update**: Within 7 days
+- **Resolution**: Depends on severity and complexity
+
+### 4. Disclosure Policy
+
+- We will acknowledge receipt of your report within 48 hours
+- We will provide regular updates on the status of the vulnerability
+- Once fixed, we will credit you (if desired) in the security advisory
+- We will coordinate public disclosure with you
+
+## Security Update Process
+
+1. **Assessment**: We assess the severity using CVSS scoring
+2. **Fix Development**: We develop and test a fix
+3. **Release**: We release a security update
+4. **Advisory**: We publish a security advisory on GitHub
+5. **Communication**: We notify users through appropriate channels
+
+## Severity Levels
+
+### Critical
+- Remote code execution
+- Authentication bypass
+- Data breach or exposure
+- **Response Time**: Immediate (within 24 hours)
+
+### High
+- Privilege escalation
+- Significant data leakage
+- Denial of service
+- **Response Time**: Within 7 days
+
+### Medium
+- Information disclosure
+- Cross-site scripting (XSS)
+- CSRF vulnerabilities
+- **Response Time**: Within 30 days
+
+### Low
+- Minor information leakage
+- Best practice violations
+- **Response Time**: Next release cycle
+
+## Known Security Considerations
+
+### Dependencies
+
+We regularly update dependencies to address security vulnerabilities. However, you should:
+
+- Keep your dependencies up to date
+- Review security advisories for our dependencies
+- Use tools like `pip-audit` or `safety` to check for known vulnerabilities
+
+### API Keys and Credentials
+
+- **Never commit API keys or credentials** to the repository
+- Use environment variables or secure configuration management
+- Rotate keys regularly
+- Use least-privilege access principles
+
+### Data Handling
+
+- Be cautious when processing untrusted data
+- Validate and sanitize all inputs
+- Use parameterized queries for database operations
+- Implement rate limiting for public APIs
+
+### Network Security
+
+- Use HTTPS for all network communications
+- Validate SSL/TLS certificates
+- Be cautious with external API calls
+- Implement proper authentication and authorization
+
+## Dependency Security Policy
+
+### Regular Updates
+
+- We monitor security advisories for all dependencies
+- We update dependencies regularly in our development branch
+- Critical security updates are backported to supported versions
+
+### Reporting Dependency Vulnerabilities
+
+If you discover a vulnerability in one of our dependencies:
+
+1. Check if it's already reported upstream
+2. Report to us if it affects Semantica specifically
+3. We will coordinate with upstream maintainers if needed
+
+### Security Scanning
+
+We use automated tools to scan for vulnerabilities:
+
+- **Dependabot**: Automated dependency updates and security alerts
+- **GitHub Security Advisories**: Vulnerability tracking
+- **Manual Reviews**: Regular security audits
+
+## Best Practices for Users
+
+1. **Keep Semantica Updated**: Always use the latest stable version
+2. **Review Dependencies**: Regularly update your project dependencies
+3. **Secure Configuration**: Use secure defaults and proper configuration
+4. **Monitor Logs**: Watch for suspicious activity
+5. **Report Issues**: Don't hesitate to report potential security issues
+
+## Security Acknowledgments
+
+We appreciate responsible disclosure. Security researchers who help us improve the security of Semantica will be:
+
+- Credited in security advisories (if desired)
+- Listed in our security acknowledgments
+- Recognized for their contribution
+
+## Contact
+
+For security-related questions or concerns:
+
+- **Email**: semantica-dev@users.noreply.github.com
+- **Subject**: [SECURITY] Brief description
+
+## Additional Resources
+
+- [OWASP Top 10](https://owasp.org/www-project-top-ten/)
+- [Python Security Best Practices](https://python.readthedocs.io/en/latest/library/security.html)
+- [GitHub Security Best Practices](https://docs.github.com/en/code-security)
+
+---
+
+**Thank you for helping keep Semantica and its users safe!**
+