feat(branding): rebrand user-facing GPUStack to MesaStack

Applied via scripts/rebrand across UI labels, page title, and all
locale strings (en/zh/ja/ru/tr). Functional references untouched:
npm package, URLs, paths, JS identifiers, GPUSTACK_ constants, and the
X-GPUStack-Model header. The backend-contract startsWith string in
llmodels/hooks keeps "GPUStack server" to stay matchable. Logo images
intentionally left unchanged for now.

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

src/pages/gpu-service/instances/config/index.ts

@@ -48,7 +48,7 @@ export const GPUStackFailedStatuses = [
 export const InstanceStatusLabelMap: Record<string, string> = {
   // === K8s Statuses ===
   ...Object.fromEntries(K8SStatuses.map((status) => [status, status])),
-  // === GPUStack Statuses no logs and events===
+  // === MesaStack Statuses no logs and events===
   [InstanceStatusValueMap.Deleting]: 'Deleting',
   [InstanceStatusValueMap.Stopping]: 'Stopping',
   [InstanceStatusValueMap.Stopped]: 'Stopped',