Move More>> toggle to edit-only, show source count instead of names in list

The row view now shows "N sources active" instead of listing every attached
source's name, and the "More »" spillover checkbox only appears in the edit
panel — it's no longer duplicated inline on every row.

frontend/src/lib/components/admin/EventsTab.svelte

@@ -23,10 +23,6 @@
 	}
 	let editForm = $state(emptyEditForm());
 
-	function sourceNames(ids: string[]) {
-		return ids.map((id) => sources.find((s) => s.id === id)?.name).filter(Boolean).join(', ') || 'No sources assigned';
-	}
-
 	async function handleAdd() {
 		if (!newEvent.name) return;
 		const created = await addEvent({
@@ -48,13 +44,6 @@
 		events = events.map((e) => (e.id === event.id ? updated : e));
 	}
 
-	// Same "More »" collapse as Category.isSpillover (see MergeTab.svelte) — an item
-	// marked here loses its own top-nav tab and shows up on /more instead.
-	async function toggleSpillover(event: AdminTrackedEvent) {
-		const updated = await updateEvent(event.id, { isSpillover: !event.isSpillover });
-		events = events.map((e) => (e.id === event.id ? updated : e));
-	}
-
 	async function handleDelete(id: string) {
 		await deleteEvent(id);
 		events = events.filter((e) => e.id !== id);
@@ -203,7 +192,7 @@
 				<div>
 					<div class="name">{event.name}</div>
 					<div class="sub">
-						{sourceNames(event.sourceIds)}
+						{event.sourceIds.length} source{event.sourceIds.length === 1 ? '' : 's'} active
 						{#if event.keywords.length > 0}
 							· matching {event.keywords.map((k) => `"${k}"`).join(', ')}
 						{/if}
@@ -211,10 +200,6 @@
 						{event.recapIntervalHours === null ? 'no recaps' : `recap every ${event.recapIntervalHours}h`}
 					</div>
 				</div>
-				<label class="spillover-toggle">
-					<input type="checkbox" checked={event.isSpillover} onchange={() => toggleSpillover(event)} />
-					More
-				</label>
 				<span class="badge" class:active={event.active} onclick={() => toggleActive(event)} role="button" tabindex="0">
 					{event.active ? 'Active' : 'Paused'}
 				</span>