feat(frontend): add OCR UI components and translations

- ScriptTypeSelect: native select for TYPEWRITER/HANDWRITING_LATIN/KURRENT
- OcrTrigger: wraps script type select + start button + confirmation dialog
- OcrProgress: SSE-based progress display with page counter and progress bar
- Paraglide translations for OCR (de/en/es): script types, trigger labels,
  confirmation dialog, progress messages, error messages
- ErrorCode type + getErrorMessage: OCR_SERVICE_UNAVAILABLE, OCR_JOB_NOT_FOUND,
  OCR_DOCUMENT_NOT_UPLOADED, OCR_PROCESSING_FAILED

All 687 frontend tests pass.

Refs #226

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

frontend/src/lib/components/OcrProgress.svelte

@@ -0,0 +1,88 @@
+<script lang="ts">
+import { m } from '$lib/paraglide/messages.js';
+
+interface Props {
+	jobId: string;
+	onDone: () => void;
+}
+
+let { jobId, onDone }: Props = $props();
+
+let status: 'running' | 'done' | 'error' = $state('running');
+let processed: number = $state(0);
+let total: number = $state(0);
+let currentPage: number = $state(0);
+let totalPages: number = $state(0);
+
+let progressPercent = $derived(total > 0 ? Math.round((processed / total) * 100) : 0);
+
+$effect(() => {
+	const source = new EventSource(`/api/ocr/jobs/${jobId}/progress`);
+
+	source.addEventListener('document', (e) => {
+		const data = JSON.parse(e.data);
+		processed = data.processed;
+		total = data.total;
+	});
+
+	source.addEventListener('page', (e) => {
+		const data = JSON.parse(e.data);
+		currentPage = data.page;
+		totalPages = data.totalPages;
+	});
+
+	source.addEventListener('done', () => {
+		status = 'done';
+		source.close();
+		onDone();
+	});
+
+	source.addEventListener('error', () => {
+		status = 'error';
+		source.close();
+	});
+
+	source.onerror = () => {
+		status = 'error';
+		source.close();
+	};
+
+	return () => {
+		source.close();
+	};
+});
+</script>
+
+{#if status === 'running'}
+	<div class="border-brand-sand rounded-sm border bg-white p-4">
+		<h3 class="mb-3 text-xs font-bold tracking-widest text-gray-400 uppercase">
+			{m.ocr_progress_heading()}
+		</h3>
+		<div class="bg-brand-sand h-2 w-full overflow-hidden rounded-full">
+			<div
+				class="h-full bg-brand-mint transition-all duration-300"
+				style="width: {progressPercent}%"
+				role="progressbar"
+				aria-valuenow={progressPercent}
+				aria-valuemin={0}
+				aria-valuemax={100}
+			></div>
+		</div>
+		<p class="mt-2 text-right text-sm text-gray-500">
+			{m.ocr_progress_page({ current: String(currentPage), total: String(totalPages) })}
+		</p>
+	</div>
+{:else if status === 'error'}
+	<div class="border-brand-sand rounded-sm border border-l-4 border-l-red-500 bg-white p-4">
+		<h3 class="mb-2 text-sm font-semibold text-red-700">
+			{m.ocr_error_heading()}
+		</h3>
+		<button
+			type="button"
+			onclick={() => { status = 'running'; }}
+			class="text-sm font-medium text-brand-navy transition-colors hover:text-brand-navy/80"
+		>
+			{m.ocr_error_retry()}
+		</button>
+	</div>
+{/if}