feat(deploy): async compose-up for instant UI feedback (v0.28.2)

Deploy API now returns immediately after validation + config save.
docker compose up -d runs in a background goroutine so the UI shows
progress during image pulls instead of blocking for 30-60s.

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

controller/internal/web/templates/deploy.html

@@ -632,8 +632,23 @@ document.getElementById('deploy-form').addEventListener('submit', async function
                 var sd = await sr.json();
                 if (!sd.ok || !sd.data) return;
                 var state = sd.data.state;
+                var deployError = sd.data.deploy_error;
 
-                if (state === 'running') {
+                if (deployError) {
+                    // Async compose-up failed
+                    clearInterval(pollTimer);
+                    setStep(stepContainers, 'error', 'Telepítés sikertelen');
+                    setStep(stepHealth, 'error');
+                    progressEl.querySelector('h3').textContent = 'Telepítés sikertelen';
+                    resultEl.innerHTML = '<div class="alert alert-error" style="margin-top:1rem">' +
+                        'A telepítés nem sikerült: ' + deployError +
+                        '</div><a href="/stacks/' + stackName + '/logs" class="btn btn-outline" style="margin-top:.75rem">Naplók megtekintése</a>' +
+                        ' <a href="/stacks" class="btn btn-primary" style="margin-top:.75rem">Alkalmazások</a>';
+                    resultEl.style.display = 'block';
+                } else if (state === 'deploying') {
+                    // Compose up in progress (pulling images, creating containers)
+                    setStep(stepContainers, 'active', 'Képek letöltése, konténerek indítása...');
+                } else if (state === 'running') {
                     clearInterval(pollTimer);
                     setStep(stepContainers, 'done', 'Konténerek elindultak');
                     setStep(stepHealth, 'done', 'Alkalmazás kész!');