Add Windows support: GUI installer and system tray manager

Added complete Windows deployment capability:

  - windows/agent-manager.py: System tray GUI application
    * Configuration editor (no manual JSON editing)
    * Log viewer with refresh/tail
    * Service management (start/stop/restart)
    * Status monitoring dashboard
    * Windows toast notifications

  - windows/installer.iss: Inno Setup installer script
    * Graphical one-click installer
    * Service registration via NSSM
    * Start menu shortcuts
    * Uninstaller support

  - install-windows.ps1: PowerShell installer (legacy/cli)
    * Automated installation without GUI
    * Service registration (NSSM or Task Scheduler)

  - windows/build.py: Automated build script
    * PyInstaller builds for agent and manager
    * Inno Setup compilation
    * Dependency checking

  - Modified hermes_node_agent.py:
    * Fixed duplicate PosixComputerController class
    * Cleaned up code structure

  - Modified install.sh:
    * Simplified user-friendly output
    * Better error handling

The Windows agent includes:
  * PowerShell-based command execution
  * sexec.ps1 permission system (matches Linux)
  * Windows Service integration (NSSM)
  * Same WebSocket protocol (WSS)

Documentation: WINDOWS_DEPLOYMENT.md, WINDOWS_INSTALL.md

See COMPLETE_DEPLOYMENT.md for full overview.

Hermes Agent integration:
  * Works with plugins/node_gateway.py
  * Same API as Linux nodes
  * hermes node windows-pc exec "command"