Add shared EventActivity component

src/app/components/EventActivity.svelte

@@ -0,0 +1,31 @@
+<script lang="ts">
+  import {onMount} from "svelte"
+  import {max} from "@welshman/lib"
+  import {COMMENT} from "@welshman/util"
+  import {deriveEvents} from "@welshman/store"
+  import type {TrustedEvent} from "@welshman/util"
+  import {formatTimestampRelative, repository, load} from "@welshman/app"
+  import {notifications} from "@app/notifications"
+  import Icon from "@lib/components/Icon.svelte"
+
+  const {url, path, event}: {url: string; path: string; event: TrustedEvent} = $props()
+
+  const filters = [{kinds: [COMMENT], "#E": [event.id]}]
+  const replies = deriveEvents(repository, {filters})
+  const lastActive = $derived(max([...$replies, event].map(e => e.created_at)))
+
+  onMount(() => {
+    load({relays: [url], filters})
+  })
+</script>
+
+<div class="flex-inline btn btn-neutral btn-xs gap-1 rounded-full">
+  <Icon icon="reply" />
+  <span>{$replies.length} {$replies.length === 1 ? "reply" : "replies"}</span>
+</div>
+<div class="btn btn-neutral btn-xs relative hidden rounded-full sm:flex">
+  {#if $notifications.has(path)}
+    <div class="h-2 w-2 rounded-full bg-primary"></div>
+  {/if}
+  Active {formatTimestampRelative(lastActive)}
+</div>