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/logic/mapper.go

@@ -195,6 +195,7 @@ func toAPIProject(project design.Project) types.Project {
 		SnapshotId:   project.SnapshotID,
 		Canvas:       project.Canvas,
 		LastThreadId: project.LastThreadID,
+		BrandKitId:   project.BrandKitID,
 		Viewport:     toAPIView(project.Viewport),
 		Nodes:        toAPINodes(project.Nodes),
 		Connections:  toAPIConnections(project.Connections),
@@ -206,13 +207,14 @@ func toAPISummaries(items []design.ProjectSummary) []types.ProjectSummary {
 	resp := make([]types.ProjectSummary, 0, len(items))
 	for _, item := range items {
 		resp = append(resp, types.ProjectSummary{
-			Id:        item.ID,
-			UserId:    item.UserID,
-			Title:     item.Title,
-			Brief:     item.Brief,
-			Status:    string(item.Status),
-			Thumbnail: item.Thumbnail,
-			UpdatedAt: formatTime(item.UpdatedAt),
+			Id:         item.ID,
+			UserId:     item.UserID,
+			Title:      item.Title,
+			Brief:      item.Brief,
+			Status:     string(item.Status),
+			Thumbnail:  item.Thumbnail,
+			BrandKitId: item.BrandKitID,
+			UpdatedAt:  formatTime(item.UpdatedAt),
 		})
 	}
 	return resp