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}

frontend/src/lib/components/OcrTrigger.svelte

@@ -0,0 +1,49 @@
+<script lang="ts">
+import { untrack } from 'svelte';
+import * as m from '$lib/paraglide/messages.js';
+import { getConfirmService } from '$lib/services/confirm.svelte';
+import ScriptTypeSelect from './ScriptTypeSelect.svelte';
+
+interface Props {
+	existingBlockCount: number;
+	storedScriptType: string;
+	onTrigger: (scriptType: string) => void;
+}
+
+let { existingBlockCount, storedScriptType, onTrigger }: Props = $props();
+
+const { confirm } = getConfirmService();
+
+let selectedScriptType: string = $state(
+	untrack(() => (storedScriptType && storedScriptType !== 'UNKNOWN' ? storedScriptType : ''))
+);
+
+async function handleClick() {
+	if (!selectedScriptType) return;
+
+	if (existingBlockCount > 0) {
+		const confirmed = await confirm({
+			title: m.ocr_confirm_title(),
+			body: m.ocr_confirm_body({ count: String(existingBlockCount) }),
+			confirmLabel: m.ocr_confirm_btn(),
+			destructive: true
+		});
+		if (!confirmed) return;
+	}
+
+	onTrigger(selectedScriptType);
+}
+</script>
+
+<div class="flex flex-col gap-3">
+	<ScriptTypeSelect bind:value={selectedScriptType} />
+	<button
+		type="button"
+		disabled={!selectedScriptType}
+		title={!selectedScriptType ? m.ocr_trigger_btn_disabled() : undefined}
+		onclick={handleClick}
+		class="min-h-[44px] w-full rounded-sm bg-brand-navy font-sans text-sm font-medium text-white transition-colors hover:bg-brand-navy/90 disabled:cursor-not-allowed disabled:opacity-50"
+	>
+		{m.ocr_trigger_btn()}
+	</button>
+</div>

frontend/src/lib/components/ScriptTypeSelect.svelte

@@ -0,0 +1,27 @@
+<script lang="ts">
+import * as m from '$lib/paraglide/messages.js';
+
+interface Props {
+	value: string;
+	disabled?: boolean;
+}
+
+let { value = $bindable(), disabled = false }: Props = $props();
+</script>
+
+<div>
+	<label for="script-type-select" class="text-xs font-bold tracking-widest text-gray-400 uppercase">
+		{m.ocr_trigger_label()}
+	</label>
+	<select
+		id="script-type-select"
+		bind:value={value}
+		disabled={disabled}
+		class="border-brand-sand min-h-[44px] w-full rounded-sm border bg-white px-3 py-2 font-serif text-sm text-brand-navy focus:ring-2 focus:ring-brand-mint focus:outline-none"
+	>
+		<option value="" disabled>{m.ocr_trigger_select_placeholder()}</option>
+		<option value="TYPEWRITER">{m.ocr_script_type_typewriter()}</option>
+		<option value="HANDWRITING_LATIN">{m.ocr_script_type_handwriting_latin()}</option>
+		<option value="HANDWRITING_KURRENT">{m.ocr_script_type_handwriting_kurrent()}</option>
+	</select>
+</div>