feat: Add validation viewing functionality and UI updates

- Implemented a new function to mark validations as viewed by the user, updating the validation state accordingly.
- Added a new API endpoint for marking validations as viewed, integrated with the existing GitHub routes.
- Enhanced the sidebar to display the count of unviewed validations, providing real-time updates.
- Updated the GitHub issues view to mark validations as viewed when issues are accessed, improving user interaction.
- Introduced a visual indicator for unviewed validations in the issue list, enhancing user awareness of pending validations.

apps/ui/src/lib/electron.ts

@@ -227,6 +227,11 @@ export interface GitHubAPI {
     isStale?: boolean;
     error?: string;
   }>;
+  /** Mark a validation as viewed by the user */
+  markValidationViewed: (
+    projectPath: string,
+    issueNumber: number
+  ) => Promise<{ success: boolean; error?: string }>;
   /** Subscribe to validation events */
   onValidationEvent: (callback: (event: IssueValidationEvent) => void) => () => void;
 }