fix: bump comment text to text-base + reload annotations on block delete

Comment text:
- Body and quote bumped from text-sm (14px) to text-base (16px)
  to visually match the font-sans author name at text-sm

Annotation reload on delete:
- Add annotationReloadKey prop through DocumentViewer → PdfViewer
- Increment key after block delete in +page.svelte
- PdfViewer reloads annotations when key changes
- Annotation rectangle disappears immediately, not just after refresh

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

frontend/src/lib/components/CommentThread.svelte

@@ -240,7 +240,7 @@ onMount(() => {
 							{/if}
 						</div>
 						{#if parsed.quote}
-							<div class="my-1 border-l-2 border-line pl-2 font-serif text-sm text-ink-3 italic">
+							<div class="my-1 border-l-2 border-line pl-2 font-serif text-base text-ink-3 italic">
 								&ldquo;{parsed.quote}&rdquo;
 							</div>
 						{/if}
@@ -258,7 +258,7 @@ onMount(() => {
 							<!-- svelte-ignore a11y_no_static_element_interactions -->
 							<div class="relative" onclick={() => { if (isOwn(msg)) startEdit(msg); }}>
 								<p
-									class="font-serif text-sm leading-relaxed text-ink-2 {isOwn(msg) ? '-mx-1 cursor-text rounded px-1 transition-colors hover:bg-surface' : ''}"
+									class="font-serif text-base leading-relaxed text-ink-2 {isOwn(msg) ? '-mx-1 cursor-text rounded px-1 transition-colors hover:bg-surface' : ''}"
 								>
 									<!-- eslint-disable-next-line svelte/no-at-html-tags -- renderBody escapes all HTML before injecting mention links -->
 									{@html renderBody(parsed.body, msg.mentionDTOs ?? [])}