fix(build): 署名注入改走 Node 规范化 + for /f 直读文件

上一版用 PowerShell 管道读取：PS 5.1 的 Get-Content 默认按 ANSI 读，输出再经
cmd(chcp 65001) 解码一次，中文署名被转成乱码 —— 日志写着 injected，但 exe 里的
字节与预期不符（实测 sig_in_exe=False）。
改为 deploy/prepare-signature.mjs 读 UTF-8 并剥 BOM/空白，写出 signature.build.txt
（gitignore），build.bat 用 for /f 直接读文件（不经过任何编码转换）。
另加一条 findstr 自检：注入后若 exe 里找不到署名就打印 [warn]。

deploy/build.bat

@@ -30,13 +30,16 @@ echo === [3/4] server build ===
 cd server
 if not exist ..\dist mkdir ..\dist
 REM internal signature is injected from a machine-local file (gitignored, never in repo).
-REM set /p returns empty under chcp 65001, so read the first line with for /f instead.
-REM PowerShell reads the file as text and strips a BOM; for /f file-read does not.
+REM set /p returns empty under chcp 65001; PowerShell piping re-encodes the text and
+REM corrupts non-ASCII. So a Node script normalizes it (BOM/whitespace stripped) into
+REM deploy\signature.build.txt, and for /f reads that file directly (no re-encoding).
+node ..\deploy\prepare-signature.mjs || exit /b 1
 set "INTERNAL_SIGNATURE="
-if exist "..\deploy\signature.local.txt" for /f "usebackq delims= eol=" %%A in (`powershell -NoProfile -Command "Get-Content -LiteralPath '..\deploy\signature.local.txt' -TotalCount 1"`) do if not defined INTERNAL_SIGNATURE set "INTERNAL_SIGNATURE=%%A"
+if exist "..\deploy\signature.build.txt" for /f "usebackq delims= eol=" %%A in ("..\deploy\signature.build.txt") do if not defined INTERNAL_SIGNATURE set "INTERNAL_SIGNATURE=%%A"
 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
   echo   internal signature injected
 ) else (
   go build -o ..\dist\scoreboard.exe . || exit /b 1