feat(channel): integrate channel functionality into post management

- Added Channel support in Post model, including ChannelID field in PostRequest and PostResponse DTOs.
- Updated PostService and PostRepository to handle channel-specific logic for creating and listing posts.
- Introduced ChannelRepository and ChannelService, along with corresponding handlers for managing channels.
- Enhanced router to include routes for channel management and public channel listing.
- Seeded default channels in the database during initialization.

internal/model/channel.go

@@ -0,0 +1,32 @@
+package model
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+	"gorm.io/gorm"
+)
+
+// Channel 频道配置（用于帖子分区）
+type Channel struct {
+	ID          string    `json:"id" gorm:"type:varchar(36);primaryKey"`
+	Name        string    `json:"name" gorm:"type:varchar(100);not null"`
+	Slug        string    `json:"slug" gorm:"type:varchar(100);uniqueIndex;not null"`
+	Description string    `json:"description" gorm:"type:varchar(255)"`
+	SortOrder   int       `json:"sort_order" gorm:"default:0;index"`
+	IsActive    bool      `json:"is_active" gorm:"default:true;index"`
+	CreatedAt   time.Time `json:"created_at" gorm:"autoCreateTime"`
+	UpdatedAt   time.Time `json:"updated_at" gorm:"autoUpdateTime"`
+}
+
+func (c *Channel) BeforeCreate(tx *gorm.DB) error {
+	if c.ID == "" {
+		c.ID = uuid.New().String()
+	}
+	return nil
+}
+
+func (Channel) TableName() string {
+	return "channels"
+}
+

internal/model/init.go

@@ -98,6 +98,7 @@ func autoMigrate(db *gorm.DB) error {
 		// 帖子相关
 		&Post{},
 		&PostImage{},
+		&Channel{},
 
 		// 评论相关
 		&Comment{},
@@ -178,6 +179,11 @@ func autoMigrate(db *gorm.DB) error {
 		return fmt.Errorf("failed to seed permissions: %w", err)
 	}
 
+	// 初始化频道配置种子数据
+	if err := seedChannels(db); err != nil {
+		return fmt.Errorf("failed to seed channels: %w", err)
+	}
+
 	return nil
 }
 
@@ -315,6 +321,43 @@ func seedPermissions(db *gorm.DB) error {
 	return nil
 }
 
+// seedChannels 初始化频道种子数据（按 slug 幂等）
+func seedChannels(db *gorm.DB) error {
+	defaultChannels := []Channel{
+		{Name: "跳蚤市场", Slug: "market", Description: "二手交易与闲置发布", SortOrder: 10, IsActive: true},
+		{Name: "课程交流", Slug: "courses", Description: "课程资料、选课与学习讨论", SortOrder: 20, IsActive: true},
+		{Name: "工作实习", Slug: "jobs", Description: "实习、内推与求职信息", SortOrder: 30, IsActive: true},
+		{Name: "考研考公", Slug: "exam", Description: "备考经验、资料与互助", SortOrder: 40, IsActive: true},
+		{Name: "保研出国", Slug: "graduate-abroad", Description: "保研、留学申请与经验分享", SortOrder: 50, IsActive: true},
+	}
+
+	for _, item := range defaultChannels {
+		var existing Channel
+		err := db.Where("slug = ?", item.Slug).First(&existing).Error
+		if err == nil {
+			updates := map[string]any{
+				"name":        item.Name,
+				"description": item.Description,
+				"sort_order":  item.SortOrder,
+				"is_active":   item.IsActive,
+			}
+			if uerr := db.Model(&existing).Updates(updates).Error; uerr != nil {
+				return uerr
+			}
+			continue
+		}
+		if err != nil && err != gorm.ErrRecordNotFound {
+			return err
+		}
+		if cerr := db.Create(&item).Error; cerr != nil {
+			return cerr
+		}
+	}
+
+	zap.L().Info("Seeded channels successfully", zap.Int("count", len(defaultChannels)))
+	return nil
+}
+
 // CloseDB 关闭数据库连接
 func CloseDB(db *gorm.DB) {
 	if sqlDB, err := db.DB(); err == nil {

internal/model/post.go

@@ -22,7 +22,7 @@ const (
 type Post struct {
 	ID          string `json:"id" gorm:"type:varchar(36);primaryKey"`
 	UserID      string `json:"user_id" gorm:"type:varchar(36);index;index:idx_posts_user_status_created,priority:1;not null"`
-	CommunityID string `json:"community_id" gorm:"type:varchar(36);index"`
+	ChannelID *string `json:"channel_id,omitempty" gorm:"type:varchar(36);index"`
 	Title       string `json:"title" gorm:"type:varchar(200);not null"`
 	Content     string `json:"content" gorm:"type:text;not null"`