Rename mobile app directories (client_app -> client, staff_app -> staff) and normalize changelog version tags from `0.0.1-M3` to `v0.0.1-m3` in the affected CHANGELOG.md files to standardize folder naming and version formatting.
Rename mobile app directories (client_app -> client, staff_app -> staff) and normalize changelog version tags from `0.0.1-M3` to `v0.0.1-m3` in the affected CHANGELOG.md files to standardize folder naming and version formatting.