fix: rewrite package.bat for reliable Windows builds

package.bat

@@ -2,14 +2,18 @@
 setlocal
 
 set VERSION=1.0.0
-for /f "tokens=2 delims==" %%I in ('wmic os get localdatetime /value') do set datetime=%%I
-set BUILD_TIME=%datetime:~0,4%-%datetime:~4,2%-%datetime:~6,2% %datetime:~8,2%:%datetime:~10,2%:%datetime:~12,2%
-set LDFLAGS=-s -w -X "main.Version=%VERSION%" -X "main.BuildTime=%BUILD_TIME%"
+
+REM -- 获取干净时间戳 (powershell) --
+for /f %%I in ('powershell -NoProfile -Command "Get-Date -Format 'yyyy-MM-dd HH:mm:ss'"') do set BUILD_TIME=%%I
+
+set GOOS=windows
+set GOARCH=amd64
+set LDFLAGS=-s -w -X main.Version=%VERSION% -X main.BuildTime=%BUILD_TIME%
 
 echo.
 echo  Building Server...
-mkdir dist\server\data 2>nul
-set GOOS=windows&& set GOARCH=amd64&& go build -ldflags "%LDFLAGS%" -o dist\server\monitor-server.exe .\cmd\server
+if not exist dist\server\data mkdir dist\server\data
+go build -ldflags "%LDFLAGS%" -o dist\server\monitor-server.exe .\cmd\server
 if %errorlevel% neq 0 (
     echo  [ERROR] Server build failed!
     pause
@@ -17,8 +21,8 @@ if %errorlevel% neq 0 (
 )
 
 echo  Building Client...
-mkdir dist\client 2>nul
-set GOOS=windows&& set GOARCH=amd64&& go build -ldflags "%LDFLAGS%" -o dist\client\monitor-client.exe .\cmd\client
+if not exist dist\client mkdir dist\client
+go build -ldflags "%LDFLAGS%" -o dist\client\monitor-client.exe .\cmd\client
 if %errorlevel% neq 0 (
     echo  [ERROR] Client build failed!
     pause
@@ -31,7 +35,4 @@ echo   Server: dist\server\monitor-server.exe
 echo   Client: dist\client\monitor-client.exe
 echo  ===================================================
 echo.
-echo  Server 分发: 复制 dist\server\ 整个文件夹
-echo  Client 分发: 复制 dist\client\ 整个文件夹
-echo.
 pause