feat: real service runtime — private networks, replicas, lifecycle, rollback

Services now reconcile into actual Docker containers instead of
bookkeeping rows:

- Per-project bridge network with service-name DNS aliases and
  ${{service.KEY}} env expansion (HOST/PORT builtins)
- Replicas, published ports, Traefik domain routing, health checks,
  restart policies persisted on the service spec; spec-hash drift
  recreates containers on redeploy
- Lifecycle API: start/stop/restart/redeploy, live runtime state,
  real image rollback (replaces the fake sleep)
- Manual scale and PUT replicas reconcile live containers; service
  and project delete remove their containers and the project network
- Canvas: real URLs, replica badges, env filter, right-click
  deploy/restart/stop/delete menu, empty state
- Service detail: real lifecycle buttons, live replica/URL strip,
  Networking editor, ${{ }} variable helper
- Fix prebuilt-image pulls racing the tag (drain the pull stream)

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/build/manager.go

@@ -93,10 +93,10 @@ func (bm *BuildManager) buildPrebuilt(ctx context.Context, req *types.BuildReque
 		return nil, fmt.Errorf("prebuilt image not specified")
 	}
 
-	// Pull the prebuilt image
+	// Pull the prebuilt image — must drain the pull stream or the daemon
+	// aborts it and the tag below races a missing image.
 	auth := registry.AuthConfig{}
-	_, err := bm.dockerClient.PullImage(ctx, req.PrebuiltImage, auth)
-	if err != nil {
+	if err := bm.dockerClient.PullImageWait(ctx, req.PrebuiltImage, auth); err != nil {
 		return nil, fmt.Errorf("failed to pull prebuilt image: %w", err)
 	}
 
@@ -104,7 +104,7 @@ func (bm *BuildManager) buildPrebuilt(ctx context.Context, req *types.BuildReque
 	if req.ImageName != "" && req.ImageTag != "" {
 		targetImage := fmt.Sprintf("%s:%s", req.ImageName, req.ImageTag)
 		if targetImage != req.PrebuiltImage {
-			err = bm.dockerClient.TagImage(ctx, req.PrebuiltImage, targetImage)
+			err := bm.dockerClient.TagImage(ctx, req.PrebuiltImage, targetImage)
 			if err != nil {
 				return nil, fmt.Errorf("failed to tag image: %w", err)
 			}
@@ -114,7 +114,7 @@ func (bm *BuildManager) buildPrebuilt(ctx context.Context, req *types.BuildReque
 
 	// Push to registry if specified
 	if req.RegistryURL != "" {
-		err = bm.dockerClient.PushImage(ctx, req.PrebuiltImage, req.RegistryURL)
+		err := bm.dockerClient.PushImage(ctx, req.PrebuiltImage, req.RegistryURL)
 		if err != nil {
 			return nil, fmt.Errorf("failed to push image: %w", err)
 		}