Rename extension from Xget for Chromium to Xget Now

Updated all references, documentation, metadata, and user-facing strings to use the new name 'Xget Now' instead of 'Xget for Chromium'. This includes changes in issue templates, workflow files, privacy and security policies, README, manifest, package.json, popup UI, and code comments/logs. Repository URLs and links have also been updated to reflect the new project name.

background.js

@@ -202,7 +202,7 @@ const DEFAULT_SETTINGS = {
 
 // 初始化扩展
 chrome.runtime.onInstalled.addListener(async () => {
-  console.log("Xget for Chromium 已安装");
+  console.log("Xget Now 已安装");
 
   // 如果尚未设置，则设置默认设置
   const settings = await chrome.storage.sync.get(DEFAULT_SETTINGS);