feat(material): add material handling and routing functionality

- Introduced MaterialHandler for managing learning materials and subjects.
- Updated router to include routes for public and admin material management.
- Enhanced database initialization with material subject and file models.
- Implemented seeding logic for material subjects and files.
- Updated wire generation to include MaterialHandler and related services.

internal/model/material.go

@@ -0,0 +1,113 @@
+package model
+
+import (
+	"database/sql/driver"
+	"encoding/json"
+	"time"
+
+	"github.com/google/uuid"
+	"gorm.io/gorm"
+)
+
+// MaterialFileType 文件类型
+type MaterialFileType string
+
+const (
+	MaterialFileTypePDF  MaterialFileType = "pdf"
+	MaterialFileTypeWord MaterialFileType = "word"
+	MaterialFileTypePPT  MaterialFileType = "ppt"
+)
+
+// MaterialStatus 资料状态
+type MaterialStatus string
+
+const (
+	MaterialStatusActive   MaterialStatus = "active"
+	MaterialStatusInactive MaterialStatus = "inactive"
+)
+
+// MaterialSubject 学科分类
+type MaterialSubject struct {
+	ID          string    `json:"id" gorm:"type:varchar(36);primaryKey"`
+	Name        string    `json:"name" gorm:"type:varchar(100);not null"`
+	Icon        string    `json:"icon" gorm:"type:varchar(50)"`         // MaterialCommunityIcons name
+	Color       string    `json:"color" gorm:"type:varchar(20)"`        // 主题色
+	Description string    `json:"description" gorm:"type:varchar(255)"` // 描述
+	SortOrder   int       `json:"sort_order" gorm:"default:0;index"`    // 排序权重
+	IsActive    bool      `json:"is_active" gorm:"default:true;index"`  // 是否启用
+	CreatedAt   time.Time `json:"created_at" gorm:"autoCreateTime"`
+	UpdatedAt   time.Time `json:"updated_at" gorm:"autoUpdateTime"`
+
+	// 关联
+	Materials []MaterialFile `json:"materials,omitempty" gorm:"foreignKey:SubjectID"`
+}
+
+// BeforeCreate 创建前生成UUID
+func (s *MaterialSubject) BeforeCreate(tx *gorm.DB) error {
+	if s.ID == "" {
+		s.ID = uuid.New().String()
+	}
+	return nil
+}
+
+func (MaterialSubject) TableName() string {
+	return "material_subjects"
+}
+
+// StringArray 字符串数组类型（用于tags）
+type StringArray []string
+
+// Value 实现 driver.Valuer 接口
+func (a StringArray) Value() (driver.Value, error) {
+	if a == nil {
+		return nil, nil
+	}
+	return json.Marshal(a)
+}
+
+// Scan 实现 sql.Scanner 接口
+func (a *StringArray) Scan(value interface{}) error {
+	if value == nil {
+		*a = nil
+		return nil
+	}
+	bytes, ok := value.([]byte)
+	if !ok {
+		return nil
+	}
+	return json.Unmarshal(bytes, a)
+}
+
+// MaterialFile 文件资料
+type MaterialFile struct {
+	ID            string          `json:"id" gorm:"type:varchar(36);primaryKey"`
+	SubjectID     string          `json:"subject_id" gorm:"type:varchar(36);index;not null"`
+	Title         string          `json:"title" gorm:"type:varchar(200);not null"`
+	Description   string          `json:"description" gorm:"type:text"`
+	FileType      MaterialFileType `json:"file_type" gorm:"type:varchar(20);not null;index"`
+	FileSize      int64           `json:"file_size" gorm:"default:0"`           // 文件大小(字节)
+	FileURL       string          `json:"file_url" gorm:"type:text;not null"`   // 文件URL
+	FileName      string          `json:"file_name" gorm:"type:varchar(255)"`   // 原始文件名
+	DownloadCount int             `json:"download_count" gorm:"default:0"`      // 下载次数
+	AuthorID      string          `json:"author_id" gorm:"type:varchar(36);index"` // 上传者ID
+	Tags          StringArray     `json:"tags" gorm:"type:json"`                  // 标签
+	Status        MaterialStatus  `json:"status" gorm:"type:varchar(20);default:active;index"` // 状态
+	CreatedAt     time.Time       `json:"created_at" gorm:"autoCreateTime;index"`
+	UpdatedAt     time.Time       `json:"updated_at" gorm:"autoUpdateTime"`
+
+	// 关联
+	Subject *MaterialSubject `json:"subject,omitempty" gorm:"foreignKey:SubjectID"`
+	Author  *User            `json:"author,omitempty" gorm:"foreignKey:AuthorID"`
+}
+
+// BeforeCreate 创建前生成UUID
+func (f *MaterialFile) BeforeCreate(tx *gorm.DB) error {
+	if f.ID == "" {
+		f.ID = uuid.New().String()
+	}
+	return nil
+}
+
+func (MaterialFile) TableName() string {
+	return "material_files"
+}