feat(server): add brand kit management and project binding

Add a brand kit domain with memory and postgres stores, a BrandKitService
for CRUD and resolution, and REST endpoints to list, upsert, and delete
brand kits. Projects can bind a brand kit whose resolved context and
reference images feed into the agent's long-term memory and design prompts.

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

server/internal/infrastructure/memory/project_repository.go

@@ -38,13 +38,14 @@ func (r *ProjectRepository) List(ctx context.Context) ([]design.ProjectSummary,
 			continue
 		}
 		items = append(items, design.ProjectSummary{
-			ID:        project.ID,
-			UserID:    project.UserID,
-			Title:     project.Title,
-			Brief:     project.Brief,
-			Status:    project.Status,
-			Thumbnail: project.Thumbnail,
-			UpdatedAt: project.UpdatedAt,
+			ID:         project.ID,
+			UserID:     project.UserID,
+			Title:      project.Title,
+			Brief:      project.Brief,
+			Status:     project.Status,
+			Thumbnail:  project.Thumbnail,
+			BrandKitID: project.BrandKitID,
+			UpdatedAt:  project.UpdatedAt,
 		})
 	}
 	return items, nil
@@ -207,6 +208,7 @@ func repositoryUserID(ctx context.Context, userID string) string {
 
 func cloneProject(project design.Project) design.Project {
 	project.UserID = repositoryUserID(context.Background(), project.UserID)
+	project.BrandImages = append([]string(nil), project.BrandImages...)
 	project.Nodes = append([]design.Node(nil), project.Nodes...)
 	project.Connections = append([]design.Connection(nil), project.Connections...)
 	project.Messages = append([]design.Message(nil), project.Messages...)