feat: initialisation du projet Olhar-API en Clean Architecture

- Spring Boot 3.4.1 + Gradle Kotlin DSL, Java 21
- Clean Architecture (domain / application / infrastructure / interfaces)
- Spring Security stateless avec JWT (JJWT 0.12.6)
- Flyway + PostgreSQL (migration V1 table users)
- SpringDoc OpenAPI / Swagger UI avec auth Bearer
- Testcontainers pour les tests d'intégration
- Use cases Register et Authenticate (endpoints POST /api/v1/auth/register et /login)
- GlobalExceptionHandler avec ProblemDetail (RFC 9457)
- docker-compose.yml pour Postgres local

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

src/main/java/com/olhar/olharapi/application/usecase/AuthenticateUserService.java

@@ -0,0 +1,32 @@
+package com.olhar.olharapi.application.usecase;
+
+import com.olhar.olharapi.application.port.in.AuthenticateUserUseCase;
+import com.olhar.olharapi.application.port.out.UserRepository;
+import com.olhar.olharapi.domain.exception.UserNotFoundException;
+import com.olhar.olharapi.domain.model.User;
+import com.olhar.olharapi.infrastructure.security.JwtService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.security.authentication.BadCredentialsException;
+import org.springframework.security.crypto.password.PasswordEncoder;
+import org.springframework.stereotype.Service;
+
+@Service
+@RequiredArgsConstructor
+public class AuthenticateUserService implements AuthenticateUserUseCase {
+
+    private final UserRepository userRepository;
+    private final PasswordEncoder passwordEncoder;
+    private final JwtService jwtService;
+
+    @Override
+    public String authenticate(Command command) {
+        User user = userRepository.findByEmail(command.email())
+                .orElseThrow(() -> new UserNotFoundException(command.email()));
+
+        if (!passwordEncoder.matches(command.password(), user.passwordHash())) {
+            throw new BadCredentialsException("Invalid credentials");
+        }
+
+        return jwtService.generateToken(user);
+    }
+}