feat: implement thread subscription and watching features #86

[David-patrick-chuks]

This PR implements a comprehensive thread subscription and notification system for vulnerabilities, as requested in Issue #86.

Key Changes:

• Backend:
  • Created Thread, ThreadReply, ThreadSubscription, and Notification models.
  • Implemented ThreadService and NotificationService for business logic.
  • Added API endpoints for threads and notifications.
  • Implemented auto-watching for vulnerability creators and repliers.
• Frontend:
  • Added a Discussion tab to the Vulnerability Details page.
  • Implemented Watch/Unwatch functionality with database persistence.
  • Added a Global Notification Center (bell icon) in the header.
  • Implemented Notification Filtering (All vs. Watching) and Direct Unwatch from the alert dropdown.
  • Added a Watched Threads section to the user profile for easy management.

Acceptance Criteria Met:

• Add "Watch" button on threads
• Auto-watch threads user creates or replies to
• Store watch status in database
• Send notifications on new replies to watched threads
• Add "Watching" filter to notification types
• Create "Watched Threads" section in profile
• Add unwatch option in notification

Closes: #86