Add Bitbucket bridge support #120
Description
Extend cross-platform support to include Bitbucket Cloud and Bitbucket Server.
Similar to Gitea/Forgejo bridge:
- Direct API calls (curl + jq) or atlassian CLI
- Import/export/sync workflows
- Provider-ID format: bitbucket:workspace/repo#123
- OAuth or App Password authentication
Research: Bitbucket REST API v2.0
Estimated effort: Similar to GitLab bridge (~2-3 days)