Fixes #52

[louvetv]

Problem

RSFC only worked with github.com and gitlab.com. Repositories on self-hosted GitLab instances (e.g. plmlab.math.cnrs.fr, forge.inrae.fr, gitlab.in2p3.fr) failed in several ways.

Changes

src/rsfc/harvesters/github_harvester.py

• Add detect_repo_type() and _is_gitlab_instance(): host-based detection that recognises self-hosted GitLab.
• Build the GitLab API base URL from the repo's actual host instead of hardcoding gitlab.com, fix some related issues.

src/rsfc/rsfc_checks/rsfc_checks.py

• uses detect_repo_type() instead of a hardcoded github.com/gitlab.com substring check.

src/rsfc/utils/rsfc_helpers.py

• uses detect_repo_type(), fix some issues.

Testing

Verified end-to-end on gitlab.in2p3.fr, forge.inrae.fr and plmlab.math.cnrs.fr.
Regression tests completed.

Known limitation

Repositories behind bot-protection proxies (e.g. Anubis) cannot be assessed, since the challenge is enforced upstream of GitLab and is not bypassed by an API token.

[dgarijo]

in theory newest versions of somef do support self hosted gitlab instances. Please @andriumon review and merge this pr.

[andriumon]

Thanks for the contribution! Everything seems fine by my side. Merging it