[APIView] Enhance API View Notification Emails with Context for Comment Replies

Currently, when a comment is replied to or resolved in API View, the notification emails sent to reviewers lack sufficient context. Reviewers often receive high volumes of emails with minimal information, making it difficult to identify which API or comment the notification refers to. This results in extra effort to locate the relevant thread and verify the resolution.

Expectations:
- Notification emails should include the full comment thread and API context.
- Emails should highlight high-severity issues and make them easily identifiable. (After issues have a severity)
- Direct links in emails should reliably take reviewers to the relevant API View item.
- Improved email content will help reviewers quickly assess and act on notifications.

No files, tests, or entry points are named. Start by locating the API View notification email generation and the handling for comment replies or resolutions, then trace how API context, comment threads, severity, and links reach the email. Done means reviewers can identify the API and thread, recognize high-severity issues, and follow a reliable link to the relevant API View item.

Written by the indexing model from the issue text.