feat: add Spring Boot ERP application with user management domain

Implement DDD-based architecture with domain, application, infrastructure,
and API layers. Includes user/role management with authentication,
RBAC permissions, audit logging, Liquibase migrations, and test suite.

CLAUDE.md

@@ -0,0 +1,47 @@
+# Effigenix ERP – Agent Guide
+
+## Stack
+Java 21, Spring Boot 3.2, PostgreSQL, Liquibase, JWT (JJWT), Maven
+
+## Architektur
+DDD + Clean Architecture. Einweg-Abhängigkeit: `domain → application → infrastructure`.
+
+```
+de.effigenix.
+├── domain.{bc}/          # Reine Geschäftslogik, KEINE Framework-Deps
+├── application.{bc}/     # Use Cases, Commands, DTOs
+├── infrastructure.{bc}/  # JPA, REST, Security, Audit
+└── shared/               # Shared Kernel (Result<E,T>, AuthorizationPort, Action)
+```
+
+Bounded Contexts: `usermanagement` (implementiert), `production`, `quality`, `inventory`, `procurement`, `sales`, `labeling`, `filiales` (Platzhalter).
+
+## Namenskonventionen
+| Artefakt | Muster | Beispiel |
+|---|---|---|
+| Use Case | `{Verb}{Noun}` | `CreateUser`, `AuthenticateUser` |
+| Command | `{Verb}{Noun}Command` | `CreateUserCommand` |
+| Domain Entity | `{Noun}` | `User`, `Role` |
+| Value Object | `{Noun}` | `UserId`, `PasswordHash`, `RoleName` |
+| Domain Error | `{Noun}Error` (sealed interface) | `UserError.UsernameAlreadyExists` |
+| JPA Entity | `{Noun}Entity` | `UserEntity` |
+| Mapper | `{Noun}Mapper` | `UserMapper` (Domain↔JPA) |
+| Repository (Domain) | `{Noun}Repository` | `UserRepository` (Interface) |
+| Repository (Impl) | `Jpa{Noun}Repository` | `JpaUserRepository` |
+| Controller | `{Noun}Controller` | `UserController` |
+| Web DTO | `{Verb}{Noun}Request` | `CreateUserRequest` |
+| Action Enum | `{Noun}Action implements Action` | `ProductionAction` |
+
+## Error Handling
+Funktional via `Result<E, T>` (`shared.common.Result`). Domain-Fehler sind sealed interfaces mit Records. Keine Exceptions im Domain/Application Layer.
+
+## Commits
+Conventional Commits. Kein `Co-Authored-By` Header – niemals.
+
+## DDD Skill
+Für neue Bounded Contexts: `/ddd-implement` Skill verwenden. Dokumentation unter `.claude/skills/ddd-implement/SKILL.md`.
+
+## Doku
+- `docs/QUICK_START.md` – Lokale Entwicklung, Docker, Seed-Daten
+- `docs/USER_MANAGEMENT.md` – Referenz-BC mit AuthorizationPort, JWT, Audit
+- `TODO.md` – Offene Aufgaben und Waves