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/handler/routes.go

@@ -94,6 +94,21 @@ func RegisterHandlers(server *rest.Server, serverCtx *svc.ServiceContext) {
 				Path:    "/auth/options",
 				Handler: getAuthOptionsHandler(serverCtx),
 			},
+			{
+				Method:  http.MethodGet,
+				Path:    "/brand-kits",
+				Handler: listBrandKitsHandler(serverCtx),
+			},
+			{
+				Method:  http.MethodPut,
+				Path:    "/brand-kits/:id",
+				Handler: upsertBrandKitHandler(serverCtx),
+			},
+			{
+				Method:  http.MethodDelete,
+				Path:    "/brand-kits/:id",
+				Handler: deleteBrandKitHandler(serverCtx),
+			},
 			{
 				Method:  http.MethodGet,
 				Path:    "/canda/chat-history",
@@ -199,6 +214,11 @@ func RegisterHandlers(server *rest.Server, serverCtx *svc.ServiceContext) {
 				Path:    "/projects/:id/agent/ws",
 				Handler: agentWebsocketHandler(serverCtx),
 			},
+			{
+				Method:  http.MethodPatch,
+				Path:    "/projects/:id/brand-kit",
+				Handler: updateProjectBrandKitHandler(serverCtx),
+			},
 			{
 				Method:  http.MethodPatch,
 				Path:    "/projects/:id/canvas",