fix: MySQL init script by selecting database

[978814197]

What

Add USE opencoze; to the MySQL init script.

Why

MySQL init logs show: ERROR 1046 (3D000) No database selected, so tables fail to create.

How

• Insert USE opencoze; after CREATE DATABASE IF NOT EXISTS opencoze ...
• File: docker/volumes/mysql/schema.sql

Testing

Not run (SQL init only).

Fixes #2605

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