Add comprehensive secrets management system for secure configuration

- Implement encrypted secrets storage with AES-128 encryption
- Add secret rotation capabilities with scheduling
- Implement comprehensive audit logging for all secret operations
- Create centralized configuration management system
- Add CLI tool for interactive secret management
- Integrate secrets with Flask configuration
- Support environment-specific configurations
- Add integrity verification for stored secrets
- Implement secure key derivation with PBKDF2

Features:
- Encrypted storage in .secrets.json
- Master key protection with file permissions
- Automatic secret rotation scheduling
- Audit trail for compliance
- Migration from environment variables
- Flask CLI integration
- Validation and sanitization

Security improvements:
- No more hardcoded secrets in configuration
- Encrypted storage at rest
- Secure key management
- Access control via authentication
- Comprehensive audit logging
- Integrity verification

CLI commands:
- manage_secrets.py init - Initialize secrets
- manage_secrets.py set/get/delete - Manage secrets
- manage_secrets.py rotate - Rotate secrets
- manage_secrets.py audit - View audit logs
- manage_secrets.py verify - Check integrity

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -61,3 +61,9 @@ tmp/
 # VAPID keys
 vapid_private.pem
 vapid_public.pem
+
+# Secrets management
+.secrets.json
+.master_key
+secrets.db
+*.key