Add workflow to automatically generate SQL database dumps (#106)

Add a GitHub Actions workflow (generate-db-dumps.yml) that can be
triggered manually to generate the demo and empty SQL database dumps
from a fully initialized OpenMRS Docker instance.

The workflow:
- Builds the OpenMRS distribution using the SDK
- Starts Docker containers for OpenMRS
- Waits for full initialization
- Runs mysqldump to create both demo and empty database dumps
- Opens a PR with the updated SQL files

Also adds scripts/generate-db-dumps.sh which handles the Docker
lifecycle and mysqldump execution for each database mode.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dkayiwa