Enhancement: Add environment variable for MySQL data volume path in docker-compose.yml

Hi AzerothCore Team,
I'm currently deploying acore-cms on a NAS environment using Docker. I've noticed a minor inconsistency in how volumes are handled, which affects users who need to store data on specific drive partitions (non-system partitions).

The Current Situation:
The **wordpress-src** volume is already configurable via the **${DOCKER_WORDPRESS_SRC_PATH}** environment variable. This works perfectly.
However, the **mysql-data** volume in the wp-db service is hardcoded as a named volume.

The Problem:
When trying to change the MySQL data path using a **docker-compose.override.yml** file, Docker still creates an empty named volume folder in the default system directory (e.g., /var/lib/docker/volumes/mysql-data) because override appends to the list rather than replacing the named volume definition. This leads to redundant folders and "orphaned" volumes on the system drive.

Proposed Solution:
Introduce a new environment variable for the MySQL data path, similar to how it's done for the WordPress source.Update the **wp-db** service in **docker-compose.yml** from:
` - mysql-data:/var/lib/mysql`
to
` - ${DOCKER_WORDPRESS_DB_PATH:-mysql-data}:/var/lib/mysql`

Benefits:
1.Flexibility: Users can easily redirect the database storage to a specific NAS folder or external drive via the .env file
2..Consistency: Aligns the configuration method with DOCKER_WORDPRESS_SRC_PATH.
3.Cleanliness: Avoids the creation of unwanted named volumes when a bind mount is preferred in an override file.

Thank you for your great work on the Acore project!