feat: Implement chunked file uploading

[WaveringAna]

This commit introduces chunked file uploading for large files, improving the reliability and user experience for uploads.

Key changes:

• Server-side (app/routes/index.ts):

  • Added POST /upload/chunk endpoint to receive individual file chunks and store them temporarily in uploads/tmp/<originalFilename>/<chunkIndex>.
  • Added POST /upload/complete endpoint to verify all chunks, assemble them into the final file in uploads/, and then integrate with existing media processing (database update, transcoding via MediaProcesser).
  • Enhanced error handling for chunk upload and assembly processes.
  • Multer configured for chunk handling.

• Client-side (app/public/js/index.js):

  • Updated FileUploader class to slice large files (configurable threshold, e.g., >20MB) into smaller chunks (e.g., 5MB).
  • Chunks are uploaded sequentially to /upload/chunk.
  • After all chunks are sent, a request is made to /upload/complete.
  • Progress indication is provided to you during chunked uploads.
  • Error handling and retry mechanism for chunk uploads.

• Error Handling & Cleanup (app/lib/cleanup.ts):

  • Added cleanupOrphanedChunks utility function to scan uploads/tmp/ and remove old, incomplete chunk directories, preventing disk space issues. This function can be triggered by a scheduled job.

• Testing (tests/chunkedUpload.test.ts):

  • Added a new test suite for the chunked upload functionality.
  • Tests cover successful end-to-end uploads, handling of missing chunks, invalid metadata, and authentication for protected routes.

This feature addresses issue #6 (chunk uploading for large files).