Fix all ESLint errors: remove unused imports, replace any types

- Remove ~60 unused imports and variables across 88 files
- Replace ~80 `any` type annotations with proper types (unknown,
  Record<string, unknown>, or specific types)
- Prefix unused callback args with underscore
- Fix unescaped JSX entities
- Lint now passes cleanly (0 errors, 2 intentional img warnings)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/notifications/notification-item.tsx

@@ -24,7 +24,7 @@ export function NotificationItem({ notification, onMarkRead }: NotificationItemP
       onMarkRead(notification.id);
     }
     if (notification.link) {
-      router.push(notification.link as any);
+      router.push(notification.link);
     }
   };