feat: Add SSH remote execution for multi-host Claude sessions

- Backend: SSH execution via spawn() with -T flag for JSON streaming
- Backend: PATH setup for non-login shells on remote hosts
- Backend: History loading via SSH (tail -n 2000 for large files)
- Frontend: Host selector UI with colored buttons in Sidebar
- Frontend: Auto-select first project when host changes
- Frontend: Pass host parameter to history and session APIs
- Docker: Install openssh-client, mount SSH keys

Enables running Claude sessions on remote hosts via SSH while
viewing them through the web UI.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -14,6 +14,9 @@ services:
       - ./config/.config/claude:/home/node/.config/claude:rw
       # Hosts configuration
       - ./config/hosts.json:/app/config/hosts.json:ro
+      # SSH keys for remote execution
+      - /home/sumdex/.ssh/id_rsa:/home/node/.ssh/id_rsa:ro
+      - /home/sumdex/.ssh/known_hosts:/home/node/.ssh/known_hosts:ro
       # Project directories for Claude to work in
       - /home/sumdex/projects:/projects:rw
       - /home/sumdex/docker:/docker:rw