feat: add auto-prompt for push notifications on app load

- Create NotificationPrompt component that appears 3 seconds after app loads
- Add to main layout so it shows on all pages (for logged-in users)
- Prompt only shows if permission not yet requested
- Users can dismiss temporarily or permanently
- Add slide-up animation for smooth appearance
- Create simplified SETUP_PUSH_NOTIFICATIONS.md guide

Users will now be automatically prompted to enable notifications
instead of having to go to the profile page.

app/globals.css

@@ -63,6 +63,17 @@ mark {
     }
   }
   
+  @keyframes slide-up {
+    from {
+      transform: translateY(100%);
+      opacity: 0;
+    }
+    to {
+      transform: translateY(0);
+      opacity: 1;
+    }
+  }
+  
   .animate-slide-in-right {
     animation: slide-in-right 0.3s ease-out;
   }
@@ -75,6 +86,10 @@ mark {
     animation: scale-in 0.2s ease-out;
   }
   
+  .animate-slide-up {
+    animation: slide-up 0.4s ease-out;
+  }
+  
   /* Smooth transitions for interactive elements */
   .transition-smooth {
     transition: all 0.2s ease-in-out;