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/errors.ts

@@ -22,6 +22,10 @@ export type ErrorCode =
 	| 'TRANSCRIPTION_BLOCK_NOT_FOUND'
 	| 'TRANSCRIPTION_BLOCK_CONFLICT'
 	| 'COMMENT_NOT_FOUND'
+	| 'OCR_SERVICE_UNAVAILABLE'
+	| 'OCR_JOB_NOT_FOUND'
+	| 'OCR_DOCUMENT_NOT_UPLOADED'
+	| 'OCR_PROCESSING_FAILED'
 	| 'UNAUTHORIZED'
 	| 'FORBIDDEN'
 	| 'VALIDATION_ERROR'
@@ -85,6 +89,14 @@ export function getErrorMessage(code: ErrorCode | string | undefined): string {
 			return m.error_transcription_block_conflict();
 		case 'COMMENT_NOT_FOUND':
 			return m.error_comment_not_found();
+		case 'OCR_SERVICE_UNAVAILABLE':
+			return m.error_ocr_service_unavailable();
+		case 'OCR_JOB_NOT_FOUND':
+			return m.error_ocr_job_not_found();
+		case 'OCR_DOCUMENT_NOT_UPLOADED':
+			return m.error_ocr_document_not_uploaded();
+		case 'OCR_PROCESSING_FAILED':
+			return m.error_ocr_processing_failed();
 		case 'UNAUTHORIZED':
 			return m.error_unauthorized();
 		case 'FORBIDDEN':