examples: generate random password for db root

[crazy-max]

fixes #272
closes #273

https://github.com/anonaddy/docker/actions/runs/9241557539/job/25423206424#step:9:66

addy_db     | 2024-05-26 07:29:26+00:00 [Note] [Entrypoint]: Temporary server started.
addy_db     | 2024-05-26 07:29:27+00:00 [Note] [Entrypoint]: GENERATED ROOT PASSWORD: DX6WyL!hIC`yy2*J(OE$P<Sq3+He/l7[
addy_db     | 2024-05-26 07:29:27+00:00 [Note] [Entrypoint]: Creating database addy
addy_db     | 2024-05-26 07:29:27+00:00 [Note] [Entrypoint]: Creating user addy
addy_db     | 2024-05-26 07:29:27+00:00 [Note] [Entrypoint]: Giving user addy access to schema addy
addy_db     | 2024-05-26 07:29:27+00:00 [Note] [Entrypoint]: Securing system users (equivalent to running mysql_secure_installation)