feat: implement upload retry functionality and enhance upload state management

Commit notes

- Added support for retrying failed uploads, including tracking retry attempts and managing upload state. - Enhanced the upload queue to store file references and relative paths for better retry capability. - Updated the UploadProgressPanel to include retry and clear failed uploads options. - Introduced methods in LibraryState to handle failed uploads and mark them for retry.

Files modified: - frontend/src/lib/api/upload.ts - frontend/src/routes/library/+page.svelte - frontend/src/routes/library/library-state.svelte.ts - frontend/src/routes/library/components/UploadDropzone.svelte - frontend/src/routes/library/components/UploadProgressPanel.svelte