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/provision-windows.sh

@@ -2,8 +2,10 @@
 # provision-windows.sh — idempotent provisioning for the Windows host runner.
 #
 # Pre-warms what compile-windows.sh would download at runtime: Flutter Windows
-# engine artifacts and pub packages. Short-circuits via a stamp file keyed to
-# the installed Flutter version, so repeat runs return immediately.
+# engine artifacts, pub packages, and the Inno Setup compiler (ISCC) used to
+# build the installer. The Flutter part short-circuits via a stamp keyed to the
+# installed Flutter version; Inno Setup is ensured on every run (cheap when
+# already present) so it self-heals independently of the Flutter stamp.
 set -euo pipefail
 
 SCRIPT_DIR="$(dirname "$0")"
@@ -15,7 +17,24 @@ STAMP="${STAMP_DIR}/provisioned-windows"
 CUR="${STAMP_DIR}/.flutter-version-win.cur"
 mkdir -p "$STAMP_DIR"
 
-# --- detection ---
+# --- ensure Inno Setup (ISCC) for building the installer (always checked) ---
+ISCC="/c/Program Files (x86)/Inno Setup 6/ISCC.exe"
+if [ ! -f "$ISCC" ]; then
+  echo "==> installing Inno Setup 6 (silent)"
+  # Canonical "latest stable" entry point (redirects to the GitHub release asset).
+  INNO_URL="https://jrsoftware.org/download.php/is.exe"
+  powershell -NoProfile -Command \
+    "Invoke-WebRequest -Uri '${INNO_URL}' -OutFile \"\$env:TEMP\\innosetup.exe\""
+  powershell -NoProfile -Command \
+    "Start-Process -Wait -FilePath \"\$env:TEMP\\innosetup.exe\" -ArgumentList '/VERYSILENT','/SUPPRESSMSGBOXES','/NORESTART','/SP-'"
+  if [ ! -f "$ISCC" ]; then
+    echo "ERROR: Inno Setup install failed — ISCC not found at '$ISCC'." >&2
+    exit 1
+  fi
+  echo "==> Inno Setup installed."
+fi
+
+# --- detection (Flutter) ---
 if ! command -v flutter >/dev/null 2>&1; then
   echo "ERROR: flutter not found on PATH. Install Flutter on this runner first." >&2
   exit 1