feat(ocr): show translated progress messages during OCR processing

Backend sends progress codes (PREPARING, LOADING, ANALYZING,
CREATING_BLOCKS:N, DONE:N, ERROR) via OcrJob.progressMessage.
Frontend translates them via Paraglide (de/en/es) and displays
below the spinner.

- V27 migration: adds progress_message column to ocr_jobs
- OcrAsyncRunner updates progress at each phase
- Poll interval reduced to 2s for snappier updates

Refs #226

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

frontend/src/routes/documents/[id]/+page.svelte

@@ -128,8 +128,30 @@ async function reviewToggle(blockId: string) {
 }
 
 let ocrRunning = $state(false);
+let ocrProgressMessage = $state('');
 let ocrPollTimer = $state<ReturnType<typeof setInterval> | null>(null);
 
+function translateOcrProgress(code: string): string {
+	if (!code) return m.ocr_progress_heading();
+	const [key, param] = code.split(':');
+	switch (key) {
+		case 'PREPARING':
+			return m.ocr_status_preparing();
+		case 'LOADING':
+			return m.ocr_status_loading();
+		case 'ANALYZING':
+			return m.ocr_status_analyzing();
+		case 'CREATING_BLOCKS':
+			return m.ocr_status_creating_blocks({ count: param ?? '0' });
+		case 'DONE':
+			return m.ocr_status_done_blocks({ count: param ?? '0' });
+		case 'ERROR':
+			return m.ocr_status_error();
+		default:
+			return code;
+	}
+}
+
 async function triggerOcr(scriptType: string) {
 	ocrRunning = true;
 	try {
@@ -157,10 +179,12 @@ function pollOcrJob(jobId: string) {
 			const res = await fetch(`/api/ocr/jobs/${jobId}`);
 			if (!res.ok) return;
 			const job = await res.json();
+			ocrProgressMessage = job.progressMessage ?? '';
 			if (job.status === 'DONE' || job.status === 'FAILED') {
 				if (ocrPollTimer) clearInterval(ocrPollTimer);
 				ocrPollTimer = null;
 				ocrRunning = false;
+				ocrProgressMessage = '';
 				await loadTranscriptionBlocks();
 				annotationReloadKey++;
 				panelMode = transcriptionBlocks.length > 0 ? 'read' : 'edit';
@@ -168,7 +192,7 @@ function pollOcrJob(jobId: string) {
 		} catch {
 			// polling is best-effort
 		}
-	}, 3000);
+	}, 2000);
 }
 
 async function createBlockFromDraw(rect: {
@@ -399,6 +423,9 @@ onMount(() => {
 							<p class="text-xs font-bold tracking-widest text-gray-400 uppercase">
 								{m.ocr_progress_heading()}
 							</p>
+							<p class="mt-2 text-sm text-ink-2">
+								{translateOcrProgress(ocrProgressMessage)}
+							</p>
 						</div>
 					{:else if panelMode === 'read'}
 						<TranscriptionReadView