fix: standardize password min length to 8 across all auth endpoints

app/Http/Requests/Api/RegisterRequest.php

@@ -12,7 +12,7 @@ class RegisterRequest extends FormRequest
     {
         return [
             'username' => ['required', 'string', 'max:50'],
-            'password' => ['required', 'string', 'min:6'],
+            'password' => ['required', 'string', 'min:8'],
             'mail' => ['required', 'email', 'max:255'],
             'look' => ['nullable', 'string'],
             'motto' => ['nullable', 'string', 'max:100'],