fix(other): prevent container startup failure by handling existing users in create script

[IrAlfred]

Using user data persistence, when we restart Cypht Docker containers, the user creation scripts exits with status 2 if the user already exists, preventing the container from starting properly.

[+] Running 3/3
 ✔ cypht                      Built                                                                       0.0s 
 ✔ Container cypht10-db-1     Running                                                                     0.0s 
 ✔ Container cypht10-cypht-1  Recreated                                                                   0.2s 
Attaching to cypht-1, db-1
cypht-1  | Cannot load Xdebug - it was already loaded
cypht-1  | 
cypht-1  | Database connection successful ...
cypht-1  | Database detected. Running migrations...
cypht-1  | Running migrations...
cypht-1  | Migrations completed.
cypht-1  | 
cypht-1  | Db setup finished
cypht-1  | Creating directory for attachments /var/lib/hm3/attachments
cypht-1  | Cannot load Xdebug - it was already loaded
cypht-1  | user admin already exists
cypht-1  | Error: Unable to create user account.
cypht-1 exited with code 2