feat(events): add client-side pagination and animations on /events\n\n- Show 5 nearest events (>= today-3d) by default\n- Add Load previous/Load later with smooth fade-slide-in for new items\n- Prevent animating existing items; preserve scroll on prepend\n- Show check-in prompt only for initial 5 events\n- Add keyframes utility in index.css

frontend/src/index.css

@@ -7,3 +7,19 @@
     @apply bg-gray-50 text-gray-900;
   }
 }
+
+@layer utilities {
+  @keyframes fade-slide-in {
+    0% {
+      opacity: 0;
+      transform: translateY(24px) scale(0.96);
+    }
+    100% {
+      opacity: 1;
+      transform: translateY(0) scale(1);
+    }
+  }
+  .animate-fade-slide-in {
+    animation: fade-slide-in 1200ms ease-out both;
+  }
+}