fix(build): 署名自检改用 Node 字节比对（findstr 在 chcp 65001 下匹配不了 UTF-8 中文）

findstr 会误报 NOT found，而实测 exe 里署名是存在的。改成 verify-signature.mjs
读字节 includes 比对，缺失时让构建硬失败。

deploy/build.bat

@@ -39,7 +39,7 @@ if exist "..\deploy\signature.build.txt" for /f "usebackq delims= eol=" %%A in (
 if defined INTERNAL_SIGNATURE (
   REM single quotes keep spaces inside the value intact for go's ldflags parser
   go build -ldflags "-X 'git.yeij.top/AskaEth/Scoreboard/server/internal/version.InternalSignature=%INTERNAL_SIGNATURE%'" -o ..\dist\scoreboard.exe . || exit /b 1
-  findstr /m /c:"%INTERNAL_SIGNATURE%" ..\dist\scoreboard.exe >nul || echo   [warn] signature NOT found in exe
+  node ..\deploy\verify-signature.mjs || exit /b 1
   echo   internal signature injected
 ) else (
   go build -o ..\dist\scoreboard.exe . || exit /b 1

deploy/verify-signature.mjs

@@ -0,0 +1,27 @@
+// 校验注入后的 exe 里确实含有署名。
+//
+// 为什么不用 findstr：它在 chcp 65001 下匹配不了 UTF-8 中文（会静默误报 NOT found），
+// 而 build.bat 又必须保持纯 ASCII。用 Node 读字节比对最稳。
+import { existsSync, readFileSync } from 'node:fs'
+import { dirname, join } from 'node:path'
+
+const root = dirname(import.meta.dirname)
+const sigFile = join(root, 'deploy', 'signature.build.txt')
+const exe = join(root, 'dist', 'scoreboard.exe')
+
+if (!existsSync(sigFile)) process.exit(0)
+
+const sig = readFileSync(sigFile, 'utf8').trim()
+if (sig === '') process.exit(0)
+
+if (!existsSync(exe)) {
+  console.error('  [warn] scoreboard.exe not found, skip signature check')
+  process.exit(0)
+}
+
+if (!readFileSync(exe).includes(Buffer.from(sig, 'utf8'))) {
+  console.error('  [ERROR] internal signature NOT found in scoreboard.exe')
+  process.exit(1)
+}
+
+console.log('  internal signature verified in exe')