feat: Introduce Nullable type for optional fields and update user DTOs accordingly

frontend/src/types/dto.ts

@@ -1,3 +1,4 @@
+import { Nullable } from "./nullable";
 // Code generated by tygo. DO NOT EDIT.
 
 //////////
@@ -167,7 +168,7 @@ export interface UserCreateDto {
   email: string;
   password: string;
   role: string;
-  companyId?: string;
+  companyId?: Nullable<string>;
   hourlyRate: number /* float64 */;
 }
 export interface UserUpdateDto {
@@ -178,6 +179,6 @@ export interface UserUpdateDto {
   email?: string;
   password?: string;
   role?: string;
-  companyId?: string;
+  companyId?: Nullable<string>;
   hourlyRate?: number /* float64 */;
 }

frontend/src/types/nullable.ts

@@ -0,0 +1 @@
+export type Nullable<T> = T | null;