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.

manifest.json

@@ -46,6 +46,13 @@
       "js": ["content/utils.js", "content/mail-163.js"],
       "all_frames": true,
       "run_at": "document_idle"
+    },
+    {
+      "matches": [
+        "https://duckduckgo.com/email/settings/autofill*"
+      ],
+      "js": ["content/utils.js", "content/duck-mail.js"],
+      "run_at": "document_idle"
     }
   ],
   "action": {