feat(training): add Paraglide i18n to training UI components and wire SegmentationTrainingCard

- Convert TrainingHistory, OcrTrainingCard, SegmentationTrainingCard, and
  TranscriptionBlock "Nur Segmentierung" badge to use Paraglide message keys
- Add availableSegBlocks to TrainingInfoResponse to expose segmentation
  block count in the training info endpoint
- Wire SegmentationTrainingCard into admin/system page below OCR training card
- Update api.ts with availableSegBlocks field

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

frontend/src/routes/admin/system/+page.svelte

@@ -2,6 +2,7 @@
 import { onDestroy } from 'svelte';
 import { m } from '$lib/paraglide/messages.js';
 import OcrTrainingCard from '$lib/components/OcrTrainingCard.svelte';
+import SegmentationTrainingCard from '$lib/components/SegmentationTrainingCard.svelte';
 import type { components } from '$lib/generated/api.js';
 
 type TrainingInfo = components['schemas']['TrainingInfoResponse'];
@@ -102,9 +103,20 @@ async function backfillFileHashes() {
 
 <div class="flex-1 overflow-y-auto p-6">
 	<div class="mx-auto max-w-2xl space-y-5">
-		<!-- OCR Training -->
+		<!-- OCR Recognition Training -->
 		<OcrTrainingCard trainingInfo={trainingInfo} />
 
+		<!-- OCR Segmentation Training -->
+		<SegmentationTrainingCard
+			trainingInfo={trainingInfo
+				? {
+						availableBlocks: trainingInfo.availableSegBlocks,
+						ocrServiceAvailable: trainingInfo.ocrServiceAvailable,
+						runs: trainingInfo.runs
+					}
+				: null}
+		/>
+
 		<!-- Backfill versions -->
 		<div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
 			<h2 class="mb-1 font-sans text-sm font-bold text-ink">{m.admin_system_backfill_heading()}</h2>