Enhance setup-certs.sh script with OS-specific installation instructions for mkcert

- Update the script to provide clear installation commands for mkcert on macOS and Ubuntu, improving user guidance for certificate setup.

deploy/setup-certs.sh

@@ -16,7 +16,8 @@ mkdir -p "$CERT_DIR"
 # 1) 确认 mkcert 已安装
 if ! command -v mkcert >/dev/null 2>&1; then
   echo "✗ 未找到 mkcert。先安装:"
-  echo "    brew install mkcert nss     # nss 是给 Firefox 用的"
+  echo "    macOS:  brew install mkcert nss     # nss 是给 Firefox 用的"
+  echo "    Ubuntu: sudo apt update && sudo apt install -y mkcert libnss3-tools"
   exit 1
 fi