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/manager.go

@@ -29,6 +29,7 @@ const (
 	StatePaused      ContainerState = "paused"
 	StateUnknown     ContainerState = "unknown"
 	StateNotDeployed ContainerState = "not_deployed"
+	StateDeploying   ContainerState = "deploying" // compose up in progress (image pull, etc.)
 	StateOrphaned    ContainerState = "orphaned"
 )
 
@@ -51,6 +52,8 @@ type Stack struct {
 	Orphaned    bool            `json:"orphaned"`   // Deployed but no catalog template
 	Containers  []ContainerInfo `json:"containers"`
 	AppConfig   *AppConfig      `json:"app_config,omitempty"`
+	Deploying   bool            `json:"deploying"`                // compose up in progress
+	DeployError string          `json:"deploy_error,omitempty"`   // last async deploy error
 	LastUpdated time.Time       `json:"last_updated"`
 }
 
@@ -250,7 +253,9 @@ func (m *Manager) refreshStatusLocked() error {
 		containers, exists := projectContainers[name]
 		if !exists {
 			stack.Containers = nil
-			if stack.Deployed {
+			if stack.Deploying {
+				stack.State = StateDeploying
+			} else if stack.Deployed {
 				stack.State = StateStopped
 			} else {
 				stack.State = StateNotDeployed