[Feature] Add possibility to pass initial admin credentials with env variables

[twinpixxx]

📃 Description

This PR adds possibility to pass admin credentials for initial startup. Closes #1597
Docs repo PR: alexjustesen/speedtest-tracker-docs#52

🪵 Changelog

➕ Added

• Environment variables

✏️ Changed

• Initial migration in which the admin user is created
• .env.example file

[DenuxPlays]

Wouldnt make Sense to accept and already hashed password?

Services like vaultwarden already do this because its way more Secure.

[twinpixxx]

@DenuxPlays it would be overcomplicated, IMHO. By design, you (as the end user) expect the password provided in the .env file to work in the web view.
I agree that it’s more secure, but with the current implementation of user management and the process for creating the default admin password, it would feel a bit odd.

[alexjustesen]

@twinpixxx couple of minor changes, also thank you for linking to the docs PR as well 👍