feat: Host CRUD complete — edit, full form fields, connect, toast

- Add UpdateHost handler + PUT /hosts/:id route
- CreateHost now accepts all fields (port, username, auth, notes)
- host_modal.html: full form with port, username, auth type toggle, edit mode
- host_list.html: edit button dispatches edit-host event with host data
- Connect button links to /terminal?host={id} for pre-selection
- Terminal page reads selected host from query param
- Toast notification system via Alpine.js events
- Add default template function for fallback values

app/backend/views/terminal.html

@@ -31,6 +31,7 @@
     </div>
   </div>
   <script id="hosts-data" type="application/json">{{.HostsJSON}}</script>
+  <script id="selected-host" type="application/json">"{{.SelectedHost}}"</script>
   <script src="/static/xterm/xterm.js"></script>
   <script src="/static/js/terminal.js"></script>
 </body>