feat: catch-all page for stopped apps, deploy controls, dashboard open button

Stopped/undeployed app subdomains now show a branded page instead of
Traefik 404. Deploy settings page gains start/stop/restart controls.
Dashboard shows "Megnyitás" button for running apps.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/cmd/controller/main.go

@@ -720,7 +720,7 @@ func main() {
 	// --- Start HTTP server ---
 	server := &http.Server{
 		Addr:         cfg.Web.Listen,
-		Handler:      mux,
+		Handler:      webServer.CatchAllMiddleware(mux),
 		ReadTimeout:  30 * time.Second,
 		WriteTimeout: 60 * time.Second,
 		IdleTimeout:  120 * time.Second,