feat(timeline): wire EventNote into EventPill + WorldBand (REQ-004)

EventPill (PERSONAL curated events) and WorldBand (HISTORICAL events) now
render the curator note immediately below the title line. Derived events
and letters carry null description so EventNote renders nothing.

Refs #844
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/timeline/EventPill.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 import EventHeader from './EventHeader.svelte';
+import EventNote from './EventNote.svelte';
 import { getAccentConfig } from './eventCardConfig';
 import type { components } from '$lib/generated/api';
 
@@ -18,7 +19,7 @@ let { entry, canWrite = false }: { entry: TimelineEntryDTO; canWrite?: boolean }
 const config = $derived(getAccentConfig(entry));
 </script>
 
-<div class="flex justify-center">
+<div class="flex flex-col items-center">
 	<div
 		class="inline-flex items-center gap-2 rounded-full bg-surface px-3 py-1 shadow-sm {config.accent ===
 		'curated'
@@ -27,4 +28,5 @@ const config = $derived(getAccentConfig(entry));
 	>
 		<EventHeader entry={entry} canWrite={canWrite} />
 	</div>
+	<EventNote description={entry.description} />
 </div>

frontend/src/lib/timeline/WorldBand.svelte

@@ -2,6 +2,7 @@
 import * as m from '$lib/paraglide/messages.js';
 import { getAccentConfig, canEditEvent } from './eventCardConfig';
 import { timelineDateLabel } from './dateLabel';
+import EventNote from './EventNote.svelte';
 import type { components } from '$lib/generated/api';
 
 type TimelineEntryDTO = components['schemas']['TimelineEntryDTO'];
@@ -61,4 +62,5 @@ const canEdit = $derived(canEditEvent(entry, canWrite));
 			<span class="sr-only">{m.btn_edit()}</span>
 		</a>
 	{/if}
+	<EventNote description={entry.description} />
 </div>