Improve initial setup experience

[YoungjaeKim]

1. set default value to .env.sample
2. set MySQL migration to true
3. [reported] describe BASE_URL clearly
4. add locale combobox to Tenant setup
5. change OS to OpenSearch in .env
6. add JWT generator link in .env comment; https://www.javainuse.com/jwtgenerator
7. add Session Password description and generator; (1) https://github.com/vvo/iron-session?tab=readme-ov-file#session-options (2) https://github.com/vvo/iron-session?tab=readme-ov-file#session-options
8. arrange and accumulate required & optional fields in .env for better reading.
9. [reported] check first tenant creation flows
10. [reported] improve Dockerfile and DockerCompose to better isolated manner

[mrgomdev]

It would be helpful to construct Getting Started process that:

• is well virtualized and encapsulated, like MySQL, ELK, or many other standalone software, running itself only from config.
• includes health checks, validations, and organizaed dependancies between sub services

Thank you for your work so far!