Moving data to SQL. This is a massive change that should not be visible to the users but will simplify a lot my work and improve the server version.

Adding the spanish translation thanks to ArielSV (many fields are not available for translation yet, they will be added in the next months)
Add strider mode when creating character (15 xp and not 10, additional distinctive feature)
Improved handling of login by the browser (e.g. saving password, pressing enter to login)

Switching library for error handling (thiserror to anyhow).
