Fix linking GitLab repos in nested subgroups

Linking a GitLab project that lived under a subgroup failed with a generic "Failed to fetch metadata" error, even when the connected token had full access. The metadata lookup was double-encoding the project path before sending it to GitLab.

• Fixed GitLab project lookups for any multi-segment path (e.g. group/subgroup/project)
• Linking repositories deep in nested GitLab groups now succeeds on the first try
• Branch listing, commit history, file content, and tree fetches across nested GitLab projects also resolve correctly