Initial commit: img-infinite-canvas AI design workbench MVP

Moteva-style AI design workbench replica. Home prompt creates a project;
the project page provides an infinite canvas with node drag, zoom/pan,
a design chat panel, history replay, image asset upload, and project
save/regenerate.

- Backend: go-zero, DDD layering, sqlc/pgx, optional PostgreSQL; memory
  or Redis cache; asynq job queue; MinIO/S3/R2/OSS object storage;
  sky-valley/pi agent runtime adapter.
- Frontend: Next.js App Router + Vite artifact build, TypeScript, i18n,
  shadcn/ui components, auth (OTP/Turnstile/Google/WeChat).
- Deploy: Docker Compose and k3s manifests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/internal/domain/design/assets.go

@@ -0,0 +1,38 @@
+package design
+
+import "context"
+
+type AssetUploadRequest struct {
+	FileName    string
+	ContentType string
+	Size        int64
+}
+
+type AssetUpload struct {
+	Driver    string
+	Bucket    string
+	ObjectKey string
+	UploadURL string
+	PublicURL string
+	Headers   map[string]string
+	ExpiresIn int64
+}
+
+type AssetObjectRequest struct {
+	FileName    string
+	ContentType string
+	Data        []byte
+}
+
+type AssetObject struct {
+	Driver    string
+	Bucket    string
+	ObjectKey string
+	PublicURL string
+}
+
+type AssetStorage interface {
+	CreateUpload(ctx context.Context, req AssetUploadRequest) (AssetUpload, error)
+	PutObject(ctx context.Context, req AssetObjectRequest) (AssetObject, error)
+	DeleteObject(ctx context.Context, publicURL string) error
+}