fix: add deployment build stamp

components/build-stamp.tsx

@@ -0,0 +1,5 @@
+import { buildCommit } from "@/lib/build-info";
+
+export function BuildStamp() {
+  return <span title={`构建提交：${buildCommit}`}>build {buildCommit.slice(0, 7)}</span>;
+}

components/site-footer.tsx

@@ -1,5 +1,6 @@
 import Link from "next/link";
 import { BrandMark } from "@/components/brand-mark";
+import { BuildStamp } from "@/components/build-stamp";
 
 export function SiteFooter() {
   return (
@@ -25,7 +26,7 @@ export function SiteFooter() {
       </div>
       <div className="container-shell flex flex-col gap-3 border-t border-line py-5 text-xs text-subtle sm:flex-row sm:items-center sm:justify-between">
         <span>© 2026 Shenzhen Kaotings Technology Co., Ltd.</span>
-        <span>Phase 1 development preview</span>
+        <span><BuildStamp /> · Phase 1 development preview</span>
       </div>
     </footer>
   );

lib/build-info.ts

@@ -0,0 +1 @@
+export const buildCommit = process.env.NEXT_PUBLIC_BUILD_COMMIT ?? "local";