feat: add data models and API structures

- Add User model with authentication fields and validation
- Add Session model for managing user sessions
- Add API response structures for consistent API responses
- Include GORM tags for database mapping and validation

models/session.go

@@ -0,0 +1,31 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+	"gorm.io/gorm"
+)
+
+type Session struct {
+	ID        uuid.UUID      `json:"id" gorm:"primaryKey;type:uuid;default:gen_random_uuid()"`
+	UserID    uuid.UUID      `json:"user_id" gorm:"not null"`
+	Revoked   bool           `json:"revoked" gorm:"not null;default:false"`
+	LoggedOut bool           `json:"logged_out" gorm:"not null;default:false"`
+	ExpiresAt time.Time      `json:"expires_at" gorm:"not null"`
+	CreatedAt time.Time      `json:"created_at" gorm:"not null;default:now()"`
+	UpdatedAt time.Time      `json:"updated_at" gorm:"not null;default:now()"`
+	DeletedAt gorm.DeletedAt `json:"deleted_at" gorm:"index;default:null"`
+
+	// Relationships
+	User User `json:"user" gorm:"foreignKey:user_id;references:id"`
+}
+
+func (s *Session) TableName() string {
+	return "sessions"
+}
+
+func (s *Session) BeforeCreate(tx *gorm.DB) (err error) {
+	s.ID = uuid.New()
+	return
+}