Implement ClientUser based on a new concept

Create a new mutable ClientEntity type and implement ClientUser on top
of it. The mutable concept is intended to replace the immutable concept
used by the ClientSchedule entities as updating immutable types in a
deep interconnected structure is a lot of hassle for little benefit.

shared/types/api.ts

@@ -1,9 +1,17 @@
 import { z } from "zod/v4-mini";
 import { defineEntity, idSchema, type Id } from "~/shared/types/common";
 
+export const apiUserTypeSchema = z.union([
+	z.literal("anonymous"),
+	z.literal("regular"),
+	z.literal("crew"),
+	z.literal("admin"),
+])
+export type ApiUserType = z.infer<typeof apiUserTypeSchema>;
+
 export interface ApiAccount {
 	id: Id,
-	type: "anonymous" | "regular" | "crew" | "admin",
+	type: ApiUserType,
 	/** Name of the account. Not present on anonymous accounts */
 	name?: string,
 	interestedEventIds?: number[],
@@ -96,6 +104,12 @@ export const apiScheduleSchema = defineEntity({
 });
 export type ApiSchedule = z.infer<typeof apiScheduleSchema>;
 
+export const apiUserSchema = defineEntity({
+	type: apiUserTypeSchema,
+	name: z.optional(z.string()),
+});
+export type ApiUser = z.infer<typeof apiUserSchema>;
+
 export interface ApiAccountUpdate {
 	type: "account-update",
 	data: ApiAccount,