feat: integrate Tesseract.js with improved language availability and font handling

- Refactored OCR page recognition to utilize a configured Tesseract worker.
- Added functions to manage font URLs and asset filenames based on language.
- Implemented language availability checks and error handling for unsupported languages.
- Enhanced PDF workflow to display available OCR languages and handle user selections.
- Introduced utility functions for resolving Tesseract asset configurations.
- Added tests for OCR functionality, font loading, and Tesseract runtime behavior.
- Updated global types to include environment variables for Tesseract and font configurations.

docs/getting-started.md

@@ -34,6 +34,9 @@ docker compose up -d
 
 Then open `http://localhost:3000` in your browser.
 
+> [!NOTE]
+> If you are preparing an air-gapped OCR deployment, you must host the OCR text-layer fonts internally in addition to the Tesseract worker, core runtime, and traineddata files. The full setup is documented in [Self-Hosting](/self-hosting/), including `VITE_OCR_FONT_BASE_URL` and the bundled `ocr-fonts/` directory.
+
 ### Option 3: Build from Source
 
 ```bash