feat: initial blog engine with multi-language, profile, and role system

- Gin + GORM + Tailwind CSS blog engine
- OS-aware config (Linux /etc/blog_go/, Windows ./win/etc/blog_go/)
- SQLite by default, MySQL support via config
- Auto-migrate database + seed admin user on first run
- Session-based auth (login/logout)
- i18n: Chinese/English with auto-detect + manual switch
- Avatar dropdown nav with click-to-toggle menu
- Profile page: avatar upload, edit info, change password
- Role system: admin (full access) and author (profile only)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

models/user.go

@@ -0,0 +1,52 @@
+package models
+
+import (
+	"time"
+
+	"golang.org/x/crypto/bcrypt"
+	"gorm.io/gorm"
+)
+
+// Account status constants.
+const (
+	StatusDisabled    = 0 // 禁用
+	StatusNormal      = 1 // 正常
+	StatusLocked      = 2 // 锁定
+	StatusUnactivated = 3 // 未激活
+)
+
+// Role constants.
+const (
+	RoleAdmin  = "admin"
+	RoleAuthor = "author"
+)
+
+// User represents a blog user (author / admin).
+type User struct {
+	gorm.Model
+	Username    string     `gorm:"uniqueIndex;not null;size:255" json:"username"`
+	Password    string     `gorm:"not null" json:"-"`
+	DisplayName string     `gorm:"size:255" json:"display_name"`
+	Avatar      string     `gorm:"size:512" json:"avatar"`
+	Birthday    *time.Time `json:"birthday"`
+	Gender      string     `gorm:"size:16" json:"gender"`
+	Email       string     `gorm:"size:255" json:"email"`
+	Status      int        `gorm:"default:1" json:"status"`
+	Role        string     `gorm:"size:32;default:author" json:"role"`
+}
+
+// SetPassword hashes the plain-text password with bcrypt and stores it.
+func (u *User) SetPassword(plain string) error {
+	hash, err := bcrypt.GenerateFromPassword([]byte(plain), bcrypt.DefaultCost)
+	if err != nil {
+		return err
+	}
+	u.Password = string(hash)
+	return nil
+}
+
+// CheckPassword compares a plain-text password against the stored bcrypt hash.
+func (u *User) CheckPassword(plain string) bool {
+	err := bcrypt.CompareHashAndPassword([]byte(u.Password), []byte(plain))
+	return err == nil
+}