[Dashboard]: Add `fenn pull` command into dashboard

[ApusBerliozi]

We need to have an opportunity to:

1 - Get all available templates as list
2 - Setting a directory, to which a template will be downloaded (with creating non-existing one, or overriding)
3 - Download the template, with progress (and result) shown in the dashboard
4 - Display fenn.yaml and main.py in the dashboard

The main point is to make ML-related job as easy as possible for a user, who has no idea how to work with CLI and other computer-science stuff.

[sarkarshrayan2-max]

Hi, I’d like to work on this issue.

I propose starting with a small backend-focused PR that:

• adds an API endpoint for listing available templates
• adds an API endpoint for downloading a selected template
• supports the target directory and force-overwrite options
• returns structured success and error responses
• includes unit tests using mocked GitHub requests and temporary directories

After that, the dashboard UI and file preview can be added either in the same issue or as a follow-up PR.

Please let me know whether this scope works for you.

[ApusBerliozi]

Hey @sarkarshrayan2-max!

Yeah, your approach is absolutely correct! You can open issues regarding each PR, and I will link them to this one

[sarkarshrayan2-max]

Thanks for confirming.

I have opened #258 for the backend implementation, covering template listing, template downloading, target-directory selection, force overwrite, structured responses, and tests.

After this PR is reviewed, I will open separate follow-up issues for:

1. Dashboard UI integration with download progress and result display
2. Displaying fenn.yaml and main.py in the dashboard

[sarkarshrayan2-max]

Thanks for confirming the split approach.

I opened the backend implementation in #258.

I also opened separate follow-up issues for:

• dashboard template-download UI: [Dashboard]: Add template download UI to dashboard #259
• fenn.yaml and main.py preview: [Dashboard]: Display fenn.yaml and main.py in dashboard #260

These together cover the remaining work for #246.

[sarkarshrayan2-max]

Both review comments have been addressed. Validation and structured API responses are now encapsulated in dedicated modules.

Ruff checks pass, and the dashboard and pull test suites pass with 57 tests.

[sarkarshrayan2-max]

Resolved the merge conflict with the latest main branch while preserving both the archive/restore dashboard functionality and the template API implementation.

Ruff checks pass, and the combined dashboard and pull test suites pass with 94 tests.