refactor(features): split entities into models/ + errors/ subdirs

All 5 features (auth, blog, marketing-pages, navigation; media has no
entities yet) now follow Lazar's pattern:
- entities/<x>.ts → entities/models/<x>.ts
- entities/errors.ts → entities/errors/<domain>.ts + errors/common.ts

Updates all import paths across factories, contracts, tests, use cases,
controllers, repositories, integrations, and src/index.ts exports.

navigation divergence: had no errors.ts; errors/header.ts +
errors/common.ts added as new forward-looking stubs.

Refactor log: docs/superpowers/refactor-logs/2026-05-05-lazar-pattern-conformance.md
Spec: §5, §9.3

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/navigation/src/infrastructure/repositories/mock-header.repository.ts

@@ -2,7 +2,7 @@ import "reflect-metadata";
 import { injectable } from "inversify";
 
 import type { IHeaderRepository } from "../../application/repositories/header-repository.interface";
-import type { Header, HeaderItem } from "../../entities/header";
+import type { Header, HeaderItem } from "../../entities/models/header";
 
 const DEFAULT_ITEMS: HeaderItem[] = [
   { label: "Home", href: "/", external: false },

packages/navigation/src/infrastructure/repositories/payload-header.repository.ts

@@ -4,7 +4,7 @@ import { getPayload } from "payload";
 import type { SanitizedConfig } from "payload";
 
 import type { IHeaderRepository } from "../../application/repositories/header-repository.interface";
-import type { Header, HeaderItem } from "../../entities/header";
+import type { Header, HeaderItem } from "../../entities/models/header";
 
 type PayloadHeaderGlobal = {
   logo?: string | number | { id: string | number } | null;