fix(transcription): auto-expand comment thread when block has comments

Comments were only shown after clicking "Kommentieren". Now:
- Load comment counts per block when blocks are loaded
- Pass commentCount prop to TranscriptionBlock
- If commentCount > 0, the comment thread is expanded by default
- If commentCount is 0, thread stays collapsed behind the button

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

frontend/src/lib/components/TranscriptionEditView.svelte

@@ -30,10 +30,34 @@ let activeBlockId: string | null = $state(null);
 let saveStates = new SvelteMap<string, SaveState>();
 let debounceTimers = new SvelteMap<string, ReturnType<typeof setTimeout>>();
 let pendingTexts = new SvelteMap<string, string>();
+let commentCounts = new SvelteMap<string, number>();
 
 let sortedBlocks = $derived([...blocks].sort((a, b) => a.sortOrder - b.sortOrder));
 let hasBlocks = $derived(blocks.length > 0);
 
+async function loadCommentCounts() {
+	for (const block of blocks) {
+		try {
+			const res = await fetch(
+				`/api/documents/${documentId}/transcription-blocks/${block.id}/comments`
+			);
+			if (res.ok) {
+				const comments = (await res.json()) as Array<{ replies: unknown[] }>;
+				const total = comments.reduce((s, c) => s + 1 + (c.replies?.length ?? 0), 0);
+				commentCounts.set(block.id, total);
+			}
+		} catch {
+			// ignore
+		}
+	}
+}
+
+$effect(() => {
+	if (blocks.length > 0) {
+		loadCommentCounts();
+	}
+});
+
 function getSaveState(blockId: string): SaveState {
 	return saveStates.get(blockId) ?? 'idle';
 }
@@ -167,6 +191,7 @@ $effect(() => {
 						saveState={getSaveState(block.id)}
 						canComment={canComment}
 						currentUserId={currentUserId}
+						commentCount={commentCounts.get(block.id) ?? 0}
 						onTextChange={(text) => handleTextChange(block.id, text)}
 						onFocus={() => handleFocus(block.id)}
 						onDeleteClick={() => handleDelete(block.id)}