feat: implement infinite scrolling for public entity lists

Add cursor-based pagination to backend list queries
Introduce LoadMoreSentinel for intersection-based loading
Replace manual load more buttons with infinite scroll sentinel

frontend/src/components/LoadMoreSentinel.vue

@@ -0,0 +1,68 @@
+<script setup lang="ts">
+import { nextTick, onBeforeUnmount, onMounted, ref, watch } from 'vue';
+
+const props = withDefaults(
+  defineProps<{
+    active: boolean;
+    disabled?: boolean;
+    rootMargin?: string;
+  }>(),
+  {
+    disabled: false,
+    rootMargin: '360px 0px'
+  }
+);
+
+const emit = defineEmits<{
+  load: [];
+}>();
+
+const sentinel = ref<HTMLElement | null>(null);
+let observer: IntersectionObserver | null = null;
+
+function disconnectObserver() {
+  observer?.disconnect();
+  observer = null;
+}
+
+function observeSentinel() {
+  disconnectObserver();
+
+  if (!props.active || props.disabled || !sentinel.value) {
+    return;
+  }
+
+  if (typeof IntersectionObserver === 'undefined') {
+    emit('load');
+    return;
+  }
+
+  observer = new IntersectionObserver(
+    (entries) => {
+      if (entries.some((entry) => entry.isIntersecting)) {
+        emit('load');
+      }
+    },
+    { rootMargin: props.rootMargin }
+  );
+  observer.observe(sentinel.value);
+}
+
+onMounted(() => {
+  void nextTick(observeSentinel);
+});
+
+onBeforeUnmount(disconnectObserver);
+
+watch(
+  () => [props.active, props.disabled, props.rootMargin, sentinel.value],
+  () => {
+    void nextTick(observeSentinel);
+  },
+  { flush: 'post' }
+);
+</script>
+
+<template>
+  <div v-if="active" ref="sentinel" class="load-more-sentinel" aria-hidden="true"></div>
+</template>