feat: add DuckDuckGo Email Protection autofill settings

- Implemented a new content script for DuckDuckGo Email autofill functionality.
- Enhanced email polling scripts (mail-163.js, qq-mail.js, signup-page.js, vps-panel.js) to handle user flow interruptions.
- Updated utility functions to manage flow stopping and error handling.
- Introduced a stop button in the side panel for user control over ongoing processes.
- Improved UI elements and styles for better user experience, including new button states and messages.
- Adjusted the side panel to fetch DuckDuckGo email automatically and display it in the input field.

content/mail-163.js

@@ -41,9 +41,15 @@ async function persistSeenCodes() {
 
 chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
   if (message.type === 'POLL_EMAIL') {
+    resetStopState();
     handlePollEmail(message.step, message.payload).then(result => {
       sendResponse(result);
     }).catch(err => {
+      if (isStopError(err)) {
+        log(`Step ${message.step}: Stopped by user.`, 'warn');
+        sendResponse({ stopped: true, error: err.message });
+        return;
+      }
       reportError(message.step, err.message);
       sendResponse({ error: err.message });
     });