get_repos() and get_orgs() support

[maciekbanas]

Part of #754.

Implement get_repos() and get_orgs() for BitBucket Cloud:

• List repositories from workspaces via GET /2.0/repositories/{workspace}.
• Map BitBucket workspace metadata to the standardized orgs table (name, path, url, etc.).
• Produce the standard gitstats_repos table with columns: repo_id, repo_name, default_branch, stars, forks, created_at, last_activity_at, languages, issues_open, issues_closed, organization, repo_url.
• Handle contributors approximation (BitBucket has no direct contributors endpoint — derive from recent commits).
• Handle add_languages parameter (BitBucket returns a single language field per repo, not a breakdown).
• Unit tests with mocked API responses.