feat: add desktop app hot update channel

scripts/fetch-singbox.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# 下载全局代理功能所需的 sing-box 引擎二进制(macOS arm64/x64 + Windows x64)。
+# 这些二进制不进 git(太大)，打包前跑一次即可。用法： bash scripts/fetch-singbox.sh
+set -euo pipefail
+VER="${SINGBOX_VERSION:-1.13.14}"
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+DEST="$ROOT/resources/singbox"
+mkdir -p "$DEST"
+cd "$DEST"
+
+fetch() { # $1=平台目录 $2=资源名(不含扩展) $3=压缩类型 $4=包内二进制名
+  local dir="$1" asset="$2" kind="$3" bin="$4"
+  echo "▶ $dir …"
+  if [ -f "$dir/$bin" ]; then echo "  已存在，跳过"; return; fi
+  mkdir -p "$dir"
+  local url="https://github.com/SagerNet/sing-box/releases/download/v${VER}/${asset}.${kind}"
+  if [ "$kind" = "tar.gz" ]; then
+    curl -fsSL "$url" -o t.tgz && tar xzf t.tgz && mv "${asset}/${bin}" "$dir/" && rm -rf t.tgz "$asset"
+  else
+    curl -fsSL "$url" -o t.zip && unzip -qo t.zip && mv "${asset}/${bin}" "$dir/" && rm -rf t.zip "$asset"
+  fi
+  chmod +x "$dir/$bin" 2>/dev/null || true
+  echo "  ✓ $dir/$bin"
+}
+
+fetch "darwin-arm64" "sing-box-${VER}-darwin-arm64" "tar.gz" "sing-box"
+fetch "darwin-x64"   "sing-box-${VER}-darwin-amd64" "tar.gz" "sing-box"
+fetch "windows-x64"  "sing-box-${VER}-windows-amd64" "zip"   "sing-box.exe"
+echo "全部就位 ✅ （sing-box v${VER}）"