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>
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