feat(client): Windows 提供 Inno Setup 安装程序 + 下载改同源 HTTPS

- Windows 客户端打成 jiu-windows-x64-setup.exe（Inno Setup，中文向导、
  桌面/开始菜单快捷方式、卸载项），替代解压版 zip
- provision-windows.sh 自动静默安装 Inno Setup（缺则装）
- 下载 URL 从内网 HTTP Forgejo 改为 https://jiu.51yanmei.com/downloads/，
  修复 HTTPS 页面下发 http 内网地址被浏览器拦截（无法安全下载），win/mac 均生效
- deploy.sh 将安装包发布到 EC2 /opt/jiu/downloads/，nginx 新增 /downloads/ 路由

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

scripts/ci/compile-windows.sh

@@ -44,13 +44,31 @@ flutter build windows --release \
   "--dart-define=APP_VERSION=${TAG}"
 popd > /dev/null
 
-# Package the Release folder into dist/ using PowerShell Compress-Archive.
-# Source is an absolute Windows path; destination is relative to the workspace.
+# 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
+  exit 1
+fi
+
+# Run ISCC entirely under the clean build root: 32-bit ISCC would hit WOW64
+# redirection if it read the .iss / wrote output under the System32 workspace.
+cp deploy/windows/jiu-installer.iss "${BUILD_ROOT}/jiu-installer.iss"
+mkdir -p "${BUILD_ROOT}/dist"
+echo "==> building installer with Inno Setup (version ${VER})"
+"$ISCC" \
+  "/DAppVer=${VER}" \
+  "/DSrcDir=C:\\jiu-build\\client\\build\\windows\\x64\\runner\\Release" \
+  "/DOutDir=C:\\jiu-build\\dist" \
+  "C:\\jiu-build\\jiu-installer.iss"
+
+# Copy the installer back to the workspace dist/ via PowerShell (64-bit, so it
+# can write the System32 workspace path without WOW64 redirection).
 mkdir -p dist
-REL_WIN='C:\jiu-build\client\build\windows\x64\runner\Release'
-echo "==> packaging ${REL_WIN} -> dist/jiu-windows-x64.zip"
+echo "==> copying installer -> dist/jiu-windows-x64-setup.exe"
 powershell -NoProfile -Command \
-  "Compress-Archive -Path '${REL_WIN}\*' -DestinationPath 'dist\jiu-windows-x64.zip' -Force"
+  "Copy-Item 'C:\\jiu-build\\dist\\jiu-windows-x64-setup.exe' 'dist\\jiu-windows-x64-setup.exe' -Force"
 
 echo "==> compile-windows: done — dist/ contents:"
 ls -lh dist/