Initial fullstack project setup with Next.js 15, Gin, PostgreSQL and Docker Compose

- Frontend: Next.js 15 (App Router), Auth.js v5, shadcn/ui, MagicUI
- Backend: Go + Gin + GORM with layered architecture
- Auth: Local credentials login with optional Keycloak OAuth binding
- Admin: RBAC user management for admin role
- Dev: Docker Compose with hot reload for both frontend and backend
- Docker: 3-service orchestration (frontend, backend, postgres)

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

backend/internal/repository/user.go

@@ -0,0 +1,62 @@
+package repository
+
+import (
+	"evanpage-backend/internal/domain"
+	"gorm.io/gorm"
+)
+
+type UserRepository struct {
+	db *gorm.DB
+}
+
+func NewUserRepository(db *gorm.DB) *UserRepository {
+	return &UserRepository{db: db}
+}
+
+func (r *UserRepository) Create(user *domain.User) error {
+	return r.db.Create(user).Error
+}
+
+func (r *UserRepository) FindByID(id uint) (*domain.User, error) {
+	var user domain.User
+	err := r.db.First(&user, id).Error
+	return &user, err
+}
+
+func (r *UserRepository) FindByUsername(username string) (*domain.User, error) {
+	var user domain.User
+	err := r.db.Where("username = ?", username).First(&user).Error
+	return &user, err
+}
+
+func (r *UserRepository) FindByEmail(email string) (*domain.User, error) {
+	var user domain.User
+	err := r.db.Where("email = ?", email).First(&user).Error
+	return &user, err
+}
+
+func (r *UserRepository) FindByKeycloakID(keycloakID string) (*domain.User, error) {
+	var user domain.User
+	err := r.db.Where("keycloak_id = ?", keycloakID).First(&user).Error
+	return &user, err
+}
+
+func (r *UserRepository) ListAll() ([]domain.User, error) {
+	var users []domain.User
+	err := r.db.Select("id", "username", "email", "role", "keycloak_id", "created_at", "updated_at").Find(&users).Error
+	return users, err
+}
+
+func (r *UserRepository) Update(user *domain.User) error {
+	return r.db.Save(user).Error
+}
+
+func (r *UserRepository) Delete(id uint) error {
+	return r.db.Delete(&domain.User{}, id).Error
+}
+
+func (r *UserRepository) Count() (int64, error) {
+	var count int64
+	err := r.db.Model(&domain.User{}).Count(&count).Error
+	return count, err
+}