fix(ci): 健壮化 Inno Setup 安装 + 部署仅保留最新安装包

- 新增 install-innosetup.ps1：校验下载大小、检查安装程序退出码、双
  Program Files 目录定位 ISCC，修复原内联命令静默成功但没真正装上的问题
  （SYSTEM 账户下 Invoke-WebRequest 无 -UseBasicParsing + 未检查退出码）
- provision/compile-windows.sh 在两个 Program Files 目录查找 ISCC
- deploy.sh 发布安装包到 /opt/jiu/downloads 前先清旧包，仅保留最新版本

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/ci/compile-windows.sh

@@ -45,10 +45,13 @@ flutter build windows --release \
 popd > /dev/null
 
 # Package the Release folder into a Windows installer with Inno Setup (ISCC).
-# Inno Setup is installed by provision-windows.sh.
-ISCC="/c/Program Files (x86)/Inno Setup 6/ISCC.exe"
-if [ ! -f "$ISCC" ]; then
-  echo "ERROR: Inno Setup (ISCC) not found at '$ISCC'. Run provision-windows.sh first." >&2
+# Inno Setup is installed by provision-windows.sh; check both Program Files dirs.
+ISCC=""
+for c in "/c/Program Files (x86)/Inno Setup 6/ISCC.exe" "/c/Program Files/Inno Setup 6/ISCC.exe"; do
+  if [ -f "$c" ]; then ISCC="$c"; break; fi
+done
+if [ -z "$ISCC" ]; then
+  echo "ERROR: Inno Setup (ISCC) not found. Run provision-windows.sh first." >&2
   exit 1
 fi