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/PdfViewer.svelte

@@ -12,6 +12,7 @@ let {
 	documentId = '',
 	transcribeMode = false,
 	blockNumbers = {},
+	annotationReloadKey = 0,
 	activeAnnotationId = $bindable<string | null>(null),
 	onAnnotationClick,
 	onTranscriptionDraw,
@@ -21,6 +22,7 @@ let {
 	documentId?: string;
 	transcribeMode?: boolean;
 	blockNumbers?: Record<string, number>;
+	annotationReloadKey?: number;
 	activeAnnotationId?: string | null;
 	onAnnotationClick?: (id: string) => void;
 	onTranscriptionDraw?: (rect: DrawRect) => void;
@@ -208,7 +210,7 @@ $effect(() => {
 });
 
 $effect(() => {
-	if (documentId) {
+	if (documentId && annotationReloadKey >= 0) {
 		loadAnnotations(documentId);
 	}
 });