[fix] preserve macOS permissions and defer legacy migration to launch

apps/desktop/scripts/macos/pkg_x64.sh

@@ -70,7 +70,7 @@ DMG_NAME="${APP_NAME}-${PLATFORM}-${ARCH}-${APP_VERSION}.dmg"
 VOL_NAME="Install ${APP_NAME_UPPER}"
 
 echo "delete old files"
-rm -rf "${APP_BUNDLE}" "${PKG_NAME}" "${DMG_NAME}" build_pkg_temp CrossDesk_dmg_temp
+rm -rf "${APP_BUNDLE}" "${PKG_NAME}" "${DMG_NAME}" build_pkg_temp build_pkg_scripts CrossDesk_dmg_temp
 
 mkdir -p build_pkg_temp
 mkdir -p "${MACOS_DIR}" "${RESOURCES_DIR}"
@@ -132,9 +132,13 @@ find "${APP_BUNDLE}" -name '._*' -delete
 
 echo ".app created successfully."
 
-mkdir -p build_pkg_scripts
-cp "${SCRIPT_DIR}/tcc_postinstall.sh" build_pkg_scripts/postinstall
-chmod +x build_pkg_scripts/postinstall
+PKG_SCRIPT_ARGS=()
+if [[ "${CROSSDESK_MACOS_SIGN_IDENTITY:--}" != "-" ]]; then
+    mkdir -p build_pkg_scripts
+    cp "${SCRIPT_DIR}/tcc_migration_preinstall.sh" build_pkg_scripts/preinstall
+    chmod +x build_pkg_scripts/preinstall
+    PKG_SCRIPT_ARGS=(--scripts build_pkg_scripts)
+fi
 
 mkdir -p build_pkg_resources
 cat > build_pkg_resources/welcome.html <<EOF
@@ -165,7 +169,7 @@ cat > build_pkg_resources/welcome.html <<EOF
     <h1>欢迎安装 ${INSTALLER_TITLE}</h1>
     <p>CrossDesk 将安装到“应用程序”文件夹。</p>
     <p>首次启动时，CrossDesk 会引导你在系统设置中授予必要权限，包括辅助功能、录屏与系统录音等。</p>
-    <p>为避免旧版本授权残留造成状态误判，安装后可能需要重新授权。</p>
+    <p>正式签名版本正常升级时会保留已有权限。从未签名或 ad-hoc 旧版升级后，请退出旧版并启动新版。新版会迁移当前用户的录屏与辅助功能授权，并引导你重新授权。遇到异常可在“设置 → 系统权限”中重试或稍后处理。</p>
     <p>安装完成后，请从“应用程序”文件夹启动 CrossDesk。</p>
 </body>
 </html>
@@ -177,7 +181,7 @@ pkgbuild \
   --version "${APP_VERSION}" \
   --install-location "/Applications" \
   --component "${APP_BUNDLE}" \
-  --scripts build_pkg_scripts \
+  ${PKG_SCRIPT_ARGS[@]+"${PKG_SCRIPT_ARGS[@]}"} \
   build_pkg_temp/${APP_NAME}-component.pkg
 
 cat > build_pkg_temp/Distribution <<EOF