Implement account deletion with confirmation dialog

[SpeedGenius00]

Summary

This PR implements a complete account deletion feature with a safety confirmation dialog. Users can now permanently delete their accounts from the settings page, with proper cleanup of Stripe subscriptions and cascading deletion of related data.

Key Changes

• Frontend UI: Replaced disabled "Delete Account" button with an interactive confirmation dialog that requires users to type "DELETE" to confirm
• Dialog Component: Added a modal dialog with clear warnings about permanent data loss, including detections, certificates, API keys, and billing information
• API Endpoint: Created new DELETE /api/user/account route that:
  • Validates user authentication
  • Cancels active Stripe subscriptions before deletion
  • Deletes the user account with cascading deletes for related records
  • Handles errors gracefully with proper logging
• Session Management: Automatically signs out the user and redirects to home page after successful deletion
• UX Improvements: Added loading state during deletion, disabled inputs while processing, and provides clear success/error feedback via toast notifications

Implementation Details

• The confirmation dialog resets the input field when opened/closed to prevent accidental submissions
• Stripe subscription cancellation is attempted but won't block account deletion if it fails
• Database cascading deletes handle cleanup of accounts, sessions, certificates, API keys, webhooks, and notifications
• Detections are preserved with onDelete: SetNull to maintain historical records without user association
• Proper error handling with user-friendly error messages

https://claude.ai/code/session_01CgXqXQP7AZ6eXBpF69i7CW