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/stacks/deploy.go

@@ -271,41 +271,61 @@ func (m *Manager) DeployStack(req DeployRequest) (string, error) {
 		m.checkLocalImages(req.StackName, stackDir)
 	}
 
-	// Update in-memory stack state BEFORE compose up so the UI reflects
-	// "deployed" immediately (compose up can take 30-60s for image pulls).
-	// If compose up fails, we revert both disk and in-memory state below.
+	// Update in-memory stack state and mark as deploying. The compose-up
+	// runs in a goroutine so the API can return immediately and the UI
+	// shows progress via polling (image pull can take 30-60s).
 	m.mu.Lock()
 	if s, ok := m.stacks[req.StackName]; ok {
 		s.Deployed = true
+		s.Deploying = true
+		s.DeployError = ""
 		s.AppConfig = appCfg
 	}
 	m.mu.Unlock()
 
-	// Run docker compose up -d
+	// Run docker compose up -d asynchronously
+	go m.runComposeDeploy(req.StackName, stackDir, env, appCfg)
+
+	return deployWarning, nil
+}
+
+// runComposeDeploy executes docker compose up -d in background.
+// On success it refreshes status; on failure it reverts the deploy state.
+func (m *Manager) runComposeDeploy(name, stackDir string, env map[string]string, appCfg *AppConfig) {
 	start := time.Now()
 	_, composeErr := m.composeExecWithEnv(stackDir, env, "up", "-d")
+
 	if composeErr != nil {
-		m.logger.Printf("[ERROR] Stack %s deploy failed after %.1fs: %v", req.StackName, time.Since(start).Seconds(), composeErr)
+		m.logger.Printf("[ERROR] Stack %s deploy failed after %.1fs: %v", name, time.Since(start).Seconds(), composeErr)
 		// Revert in-memory state
 		m.mu.Lock()
-		if s, ok := m.stacks[req.StackName]; ok {
+		if s, ok := m.stacks[name]; ok {
 			s.Deployed = false
+			s.Deploying = false
+			s.DeployError = composeErr.Error()
 			s.AppConfig = nil
 		}
 		m.mu.Unlock()
 		// Revert disk state — keep app.yaml for debugging but mark as not deployed
 		appCfg.Deployed = false
 		_ = SaveAppConfig(stackDir, appCfg)
-		return "", fmt.Errorf("docker compose up failed: %w", composeErr)
+		return
 	}
 
-	m.logger.Printf("[INFO] Stack %s deployed successfully (took %.1fs)", req.StackName, time.Since(start).Seconds())
+	m.logger.Printf("[INFO] Stack %s deployed successfully (took %.1fs)", name, time.Since(start).Seconds())
+
+	// Clear deploying flag
+	m.mu.Lock()
+	if s, ok := m.stacks[name]; ok {
+		s.Deploying = false
+	}
+	m.mu.Unlock()
 
 	// Post-deploy container state check (async, non-blocking)
 	deployEnv := m.stackEnv(stackDir)
-	m.logPostStartStatus(req.StackName, stackDir, deployEnv)
+	m.logPostStartStatus(name, stackDir, deployEnv)
 
-	return deployWarning, m.RefreshStatus()
+	_ = m.RefreshStatus()
 }
 
 // UpdateStackConfig updates non-locked fields for a deployed stack.