feat(dashboard): add file upload support

[Hitesh-XS]

Summary

This PR adds file upload support to the Fenn dashboard, allowing users to upload datasets and other files directly through the web interface. It also adds a view of previously uploaded files with basic metadata.

Closes #249

Changes

Dashboard

• Added a new Uploads page.
• Added an Uploads entry to the dashboard sidebar.
• Added an upload form with CSRF protection.

Backend

• Added POST /api/uploads to handle file uploads.
• Added GET /api/uploads to list uploaded files.
• Added configurable upload directory support.
• Added filename sanitization using secure_filename.
• Added duplicate filename detection.
• Added server-side validation and filesystem error handling.

Frontend

• Implemented AJAX-based uploads to avoid page refreshes.
• Added upload success and error messages.
• Automatically refreshes the uploaded files list after a successful upload.
• Displays uploaded filename, file size, and last modified timestamp.

Tests

Added unit tests covering:

• Successful file upload
• Missing file validation
• Empty filename validation
• Filename sanitization
• Invalid filename handling
• Duplicate upload detection
• Listing uploaded files
• Empty upload directory
• Upload page rendering

Testing

The following checks were run successfully:

python -m pytest tests/unit/dashboard -q
python -m ruff check fenn tests
python -m ruff format --check fenn tests

[ApusBerliozi]

Hey @Hitesh-XS!

Thx 4 your work :) Please check why pre-commit is failing

[ApusBerliozi]

@Hitesh-XS, kindly resolve merge conflicts and comments above, and we will merge your PR

[Hitesh-XS]

@Hitesh-XS, kindly resolve merge conflicts and comments above, and we will merge your PR

yeah sure i will update it Rn i am in class will come to it later Thanks for quick review ;)

[ApusBerliozi]

@Hitesh-XS, kindly resolve merge conflicts and comments above, and we will merge your PR

yeah sure i will update it Rn i am in class will come to it later Thanks for quick review ;)

No worries man

Take your time :)

[ApusBerliozi]

Thx 4 fast reaction @Hitesh-XS

Kindly check why CI pipeline is failing

[Hitesh-XS]

wait did some thing went wrong ?

[ApusBerliozi]

@Hitesh-XS, we migrated to whenever today, so that was the cause of errors. Kindly check this PR

[Hitesh-XS]

@Hitesh-XS, we migrated to whenever today, so that was the cause of errors. Kindly check this PR

yeah merged and updated it

[ApusBerliozi]

Yep, everything looks cool now

Thx for your work @Hitesh-XS! Please star our project to help us grow :) You can also join our Discord if you want

[Hitesh-XS]

@ApusBerliozi Thx for giving a chance to rookie like me this was comparatively big contribution i made first time :)

[ApusBerliozi]

Congrats man :)

Everyone start with something