feat: 门户网站初始提交

- Go + Gin + html/template 服务端渲染
- 主页：Google 风格搜索框 + 导航卡片
- 后台：卡片 CRUD、搜索引擎配置、主页背景/标题配置
- 图片上传：支持 jpg/jpeg/png/gif，自动压缩，缩略图参数 ?thumb=1
- 安全：登录日志、修改密码、IP 自动封禁、IP 白名单
- 访问统计：主页访问/卡片点击/搜索追踪、实时流量、IP 统计
- SQLite 存储（modernc.org/sqlite，纯 Go）
- 内存 Session + bcrypt 密码哈希

models/admin.go

@@ -0,0 +1,75 @@
+package models
+
+import (
+	"database/sql"
+	"fmt"
+
+	"simple_portal/database"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+// Admin represents an administrator account.
+type Admin struct {
+	ID       int    `json:"id"`
+	Username string `json:"username"`
+	Password string `json:"-"` // Never expose password hash in JSON
+}
+
+// GetAdminByUsername returns an admin by username. Returns nil if not found.
+func GetAdminByUsername(username string) (*Admin, error) {
+	var a Admin
+	err := database.DB.QueryRow(
+		"SELECT id, username, password FROM admins WHERE username = ?",
+		username,
+	).Scan(&a.ID, &a.Username, &a.Password)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("failed to get admin by username: %w", err)
+	}
+	return &a, nil
+}
+
+// CreateAdmin inserts a new admin with a bcrypt-hashed password.
+func CreateAdmin(username, hashedPassword string) error {
+	_, err := database.DB.Exec(
+		"INSERT INTO admins (username, password) VALUES (?, ?)",
+		username, hashedPassword,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to create admin: %w", err)
+	}
+	return nil
+}
+
+// VerifyPassword checks if the given plain-text password matches the stored bcrypt hash.
+// Returns (matched, admin, error).
+func VerifyPassword(username, password string) (bool, *Admin, error) {
+	admin, err := GetAdminByUsername(username)
+	if err != nil {
+		return false, nil, err
+	}
+	if admin == nil {
+		return false, nil, nil
+	}
+
+	err = bcrypt.CompareHashAndPassword([]byte(admin.Password), []byte(password))
+	if err != nil {
+		return false, nil, nil
+	}
+	return true, admin, nil
+}
+
+// ChangePassword updates the password hash for an admin by ID.
+func ChangePassword(adminID int, newHashedPassword string) error {
+	_, err := database.DB.Exec(
+		"UPDATE admins SET password = ? WHERE id = ?",
+		newHashedPassword, adminID,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to change password: %w", err)
+	}
+	return nil
+}