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/user.go

@@ -0,0 +1,37 @@
+package design
+
+import (
+	"context"
+	"strings"
+
+	"github.com/google/uuid"
+)
+
+const DefaultUserID = "00000000-0000-0000-0000-000000000001"
+
+type userIDContextKey struct{}
+
+func ContextWithUserID(ctx context.Context, userID string) context.Context {
+	return context.WithValue(ctx, userIDContextKey{}, NormalizeUserID(userID))
+}
+
+func UserIDFromContext(ctx context.Context) string {
+	if ctx == nil {
+		return DefaultUserID
+	}
+	if value, ok := ctx.Value(userIDContextKey{}).(string); ok {
+		return NormalizeUserID(value)
+	}
+	return DefaultUserID
+}
+
+func NormalizeUserID(userID string) string {
+	userID = strings.TrimSpace(userID)
+	if userID == "" {
+		return DefaultUserID
+	}
+	if _, err := uuid.Parse(userID); err != nil {
+		return DefaultUserID
+	}
+	return strings.ToLower(userID)
+}