FEATURE (security): Add security md file

.github/SECURITY.md

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+# Security Policy
+
+## Reporting a Vulnerability
+
+If you discover a security vulnerability in Postgresus, please report it responsibly. **Do not create a public GitHub issue for security vulnerabilities.**
+
+### How to Report
+
+1. **Email** (preferred): Send details to [info@postgresus.com](mailto:info@postgresus.com)
+2. **Telegram**: Contact [@rostislav_dugin](https://t.me/rostislav_dugin)
+3. **GitHub Security Advisories**: Use the [private vulnerability reporting](https://github.com/RostislavDugin/postgresus/security/advisories/new) feature
+
+### What to Include
+
+- Description of the vulnerability
+- Steps to reproduce the issue
+- Potential impact and severity assessment
+- Any suggested fixes (optional)
+
+## Supported Versions
+
+| Version | Supported |
+| ------- | --------- |
+| Latest  | Yes       |
+
+We recommend always using the latest version of Postgresus. Security patches are applied to the most recent release.
+
+### PostgreSQL Compatibility
+
+Postgresus supports PostgreSQL versions 12, 13, 14, 15, 16, 17 and 18.
+
+## Response Timeline
+
+- **Acknowledgment**: Within 48-72 hours
+- **Initial Assessment**: Within 1 week
+- **Fix Timeline**: Depends on severity, but we aim to address critical issues as quickly as possible
+
+We follow a coordinated disclosure policy. We ask that you give us reasonable time to address the vulnerability before any public disclosure.
+
+## Security Features
+
+Postgresus is designed with security in mind. For full details, see our [security documentation](https://postgresus.com/security).
+
+Key features include:
+
+- **AES-256-GCM Encryption**: Enterprise-grade encryption for backup files and sensitive data
+- **Read-Only Database Access**: Postgresus uses read-only access by default and warns if write permissions are detected
+- **Role-Based Access Control**: Assign viewer, member, admin or owner roles within workspaces
+- **Audit Logging**: Track all system activities and changes made by users
+- **Zero-Trust Storage**: Encrypted backups are safe even in shared cloud storage
+
+## License
+
+Postgresus is licensed under [Apache 2.0](../LICENSE).