feat(ocr): add PREPROCESSING_PAGE progress translation and i18n strings

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

frontend/src/lib/ocr/translateOcrProgress.ts

@@ -48,6 +48,18 @@ export function translateOcrProgress(code: string): OcrProgressResult {
 				totalPages: total
 			};
 		}
+		case 'PREPROCESSING_PAGE': {
+			const current = parseInt(parts[1] ?? '0', 10);
+			const total = parseInt(parts[2] ?? '0', 10);
+			return {
+				message: m.ocr_status_preprocessing_page({
+					current: String(current),
+					total: String(total)
+				}),
+				currentPage: current,
+				totalPages: total
+			};
+		}
 		case 'ERROR':
 			return { message: m.ocr_status_error() };
 		default: