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/application/use-cases/sign-out.use-case.ts

@@ -1,7 +1,7 @@
 import type { Cookie } from "../../entities/models/cookie";
 import { authContainer } from "../../di/container";
 import { AUTH_SYMBOLS } from "../../di/symbols";
-import type { IAuthenticationService } from "../services/authentication-service.interface";
+import type { IAuthenticationService } from "../services/authentication.service.interface";
 
 export async function signOutUseCase(
   sessionId: string,