Add a Python script to push bd issues to Jira.
Features:
- Create new Jira issues from bd issues without external_ref
- Update existing Jira issues matched by external_ref
- Handle Jira workflow transitions for status changes
- Reverse field mappings (bd -> Jira) via config
- Dry-run mode for previewing changes
- Auto-update external_ref after creation (--update-refs)
Also updates README to document bidirectional sync workflow.
Closes bd-93d
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Co-Authored-By: Claude <noreply@anthropic.com>
