feat: Add SSH key authentication and custom port support

[michelroegl-brunner]

Overview

This PR adds comprehensive SSH key authentication support and custom SSH port configuration to the PVE Scripts Local application.

Features Added

🔐 SSH Key Authentication

• Multiple authentication methods: Password-only, SSH key-only, or both
• Flexible key input: Upload private key files or paste key content directly
• Passphrase support: Handle encrypted SSH keys with optional passphrases
• Secure key handling: Temporary files with proper permissions (0600) and automatic cleanup

🔌 Custom SSH Port Support

• Configurable ports: Default to port 22, but allow any valid port (1-65535)
• Database integration: Store custom ports in server configuration
• Full compatibility: Works with all SSH operations (testing, execution, file transfer)

Technical Implementation

Database Schema Updates

• Added auth_type column: password | key | both
• Added ssh_key column: Stores private key content
• Added ssh_key_passphrase column: Optional encrypted passphrase
• Added ssh_port column: Custom SSH port (default: 22)
• Backward-compatible migrations for existing servers

Backend Services

• SSH Service: Enhanced connection testing with key authentication
• SSH Execution Service: Script execution and file transfer with key auth
• Security: Proper temporary file management and cleanup
• Error Handling: Clear distinction between password and key auth failures

Frontend Components

• SSHKeyInput Component: Reusable component for key upload/paste
• ServerForm Updates: Dynamic form fields based on auth type
• Validation: SSH key format validation and port range validation
• UX: Clear authentication method selection and field visibility

API Routes

• Server Creation: Handle new authentication fields and validation
• Server Updates: Support changing authentication methods
• Connection Testing: Test both password and key authentication

Security Considerations

✅ Implemented Security Measures:

• Temporary key files created with 0600 permissions
• Automatic cleanup of temporary files after operations
• No logging or exposure of private keys in error messages
• SSH key format validation before storage
• Proper null checks and type safety

Testing

• ✅ Build process passes with no TypeScript errors
• ✅ All authentication methods tested (password, key, both)
• ✅ Custom port support verified across all SSH operations
• ✅ Backward compatibility maintained for existing servers

Breaking Changes

None - this is fully backward compatible. Existing servers will continue to work with password authentication.

Migration

Existing servers automatically migrate to use auth_type=password and ssh_port=22 with no user intervention required.

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Ready for review and testing! 🚀