Add empty database dump for RefApp 3.6.0 / Core 2.8.4 (#111)

Generated from a fresh OpenMRS Docker instance using:
- OpenMRS Core 2.8.4
- Reference Application 3.6.0 (without demo data module)
- MariaDB 10.11.7

The dump includes 230 tables with schemas fully initialized but no
demo patients (0 patients, 2 system users only). This enables the
standalone to start with a clean database, bypassing the slow
initialization process.

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

Author: dkayiwa