feat: Add SSH remote terminal support to web interface

[edenreich]

Adds SSH-based remote terminal access to the web chat interface. Users can now connect to remote servers via SSH, with auto-installation of the infer binary. Includes a Docker Compose example demonstrating both local and remote modes.

Summary of Changes

This PR enables users to:

1. Connect to remote servers via SSH from the web terminal
2. Auto-install infer binary on remote servers when missing
3. Switch between local and remote servers via a dropdown
4. Use portable Linux binaries (CGO-free) for better compatibility
5. Test with a complete Docker Compose example

Key Features

SSH Remote Mode

• Added ability to connect to remote servers via SSH from the web terminal
• Secure authentication with SSH keys or passwords
• Persistent connections with session management

Auto-installation

• Automatically installs infer binary on remote servers if missing
• Supports multiple architectures and operating systems
• Fallback mechanisms for installation failures

Web Terminal Enhancements

• Added server selection dropdown in the web interface
• Support for multiple concurrent server connections
• Improved error handling and user feedback

Portable Linux Builds

• Changed Linux builds to use CGO_ENABLED=0 for maximum compatibility
• Statically linked binaries that work on any Linux distribution
• Reduced dependency requirements on target systems

Docker Compose Example

• Complete example with local + remote Ubuntu server setup
• Environment configuration templates
• Step-by-step documentation in README.md

Technical Details

New Files:

• internal/web/ssh_client.go - SSH client implementation
• internal/web/ssh_session.go - SSH session management
• internal/web/remote_installer.go - Remote binary installation
• examples/web-terminal/ - Complete example setup

Modified Files:

• cmd/chat.go - Added SSH mode flag and configuration
• internal/web/server.go - Enhanced web server with SSH support
• internal/web/session_manager.go - Multi-server session management
• internal/web/static/app.js - Frontend server selection UI
• internal/web/templates/index.html - Updated HTML template
• Build configuration updates for portable binaries

Testing

The included Docker Compose example provides a complete test environment:

• Local infer instance for direct testing
• Remote Ubuntu server for SSH testing
• Pre-configured environment variables
• Step-by-step setup instructions

Compatibility

• Backward compatible with existing local mode
• Works with any SSH-compatible server (Linux, macOS, BSD)
• Supports both password and key-based authentication
• Portable binaries work on glibc and musl-based systems

[edenreich]

TODOs

• Create an rc and verify the auto_install works as expected
• Finalize the example using docker
• Provide another example how to control agents using kubernetes and pods from the web interface
• Make the UX a bit nicer - I don't like that the fact that there is always a first session as I enter the web interface, also I think it should be clearer each tab to what server it's running on