refactor(features): rename mock/payload/interface files per Lazar pattern

Convention now: <name>.repository.{ts,mock.ts,interface.ts}.
Renames .mock prefix to .mock suffix; drops .payload prefix from real
impls (canonical name = real impl); dot-separates the .repository
qualifier in interface filenames. Class names follow suit:
PayloadXRepository → XRepository; Mock* unchanged.

Refactor log: §1, §3
Spec: §9.1

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/auth/src/infrastructure/repositories/users.repository.mock.ts

@@ -0,0 +1,32 @@
+import "reflect-metadata";
+import { injectable } from "inversify";
+
+import type { IUsersRepository } from "../../application/repositories/users.repository.interface";
+import type { User } from "../../entities/models/user";
+
+const DEFAULT_SEED: User[] = [
+  { id: "1", username: "alice", passwordHash: "hashed_password_alice" },
+  { id: "2", username: "bob", passwordHash: "hashed_password_bob" },
+];
+
+@injectable()
+export class MockUsersRepository implements IUsersRepository {
+  private _users: User[];
+
+  constructor(initialUsers: User[] = DEFAULT_SEED) {
+    this._users = [...initialUsers];
+  }
+
+  async getUser(id: string): Promise<User | undefined> {
+    return this._users.find((u) => u.id === id);
+  }
+
+  async getUserByUsername(username: string): Promise<User | undefined> {
+    return this._users.find((u) => u.username === username);
+  }
+
+  async createUser(input: User): Promise<User> {
+    this._users.push(input);
+    return input;
+  }
+}