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/main.go

@@ -44,6 +44,12 @@ func main() {
 		}
 		return m
 	})
+	engine.AddFunc("default", func(def, val interface{}) interface{} {
+		if val == nil || val == "" {
+			return def
+		}
+		return val
+	})
 
 	app := fiber.New(fiber.Config{
 		Views: engine,
@@ -57,6 +63,7 @@ func main() {
 	app.Get("/", handler.Dashboard)
 	app.Get("/hosts", handler.DashboardList)
 	app.Post("/hosts", handler.CreateHost)
+	app.Put("/hosts/:id", handler.UpdateHost)
 	app.Delete("/hosts/:id", handler.DeleteHost)
 	app.Get("/snippets", handler.Snippets)
 	app.Get("/snippets/grid", handler.SnippetGrid)