feat: expose attachment MXC URLs in messages output (#3)

* feat: expose attachment mxc URLs in messages output

* fix: keep messages --json attachment typing compatible

* chore: ignore local .serena state

* fix: detect mxc URLs from srcURL and attachment id

* docs: add jq pipeline for downloading message attachments

* chore: bump version to 0.1.5

chore: bump version to 0.1.4

feat: rename config dir to ~/.config/beepctl/ with auto-migration

- Changed config path from beepcli to beepctl
- Auto-migrate existing config on first run (copies + removes old dir)
- Updated README with complete documentation for all commands
- Updated CONTRIBUTING.md references
- Bump version to 0.1.3

chore: add badges, fix CI, update changelog

- Add npm version and CI badges to README
- Fix CI workflow pnpm version conflict
- Add 0.1.1 to CHANGELOG