refactor: introduce Wire dependency injection and interface-based architecture

- Add Google Wire for compile-time dependency injection
- Replace concrete service types with interfaces across handlers
- Remove global state (DB, cache) in favor of constructor injection
- Split monolithic files into focused modules:
  - config: separate files for each config domain
  - dto: converters split by domain (user, post, message, group)
  - cache: separate metrics.go and redis_cache.go
- Introduce unified apperrors package with string-based error codes
- Add transaction support with context-aware repository methods
- Upgrade golang.org/x/crypto from 0.17.0 to 0.26.0

internal/handler/gorse_handler.go

@@ -11,21 +11,24 @@ import (
 	"carrot_bbs/internal/pkg/gorse"
 	"carrot_bbs/internal/pkg/response"
 
-	gorseio "github.com/gorse-io/gorse-go"
 	"github.com/gin-gonic/gin"
+	gorseio "github.com/gorse-io/gorse-go"
+	"gorm.io/gorm"
 )
 
 // GorseHandler Gorse推荐处理器
 type GorseHandler struct {
 	importPassword string
 	gorseConfig    config.GorseConfig
+	db             *gorm.DB
 }
 
 // NewGorseHandler 创建Gorse处理器
-func NewGorseHandler(cfg config.GorseConfig) *GorseHandler {
+func NewGorseHandler(cfg config.GorseConfig, db *gorm.DB) *GorseHandler {
 	return &GorseHandler{
 		importPassword: cfg.ImportPassword,
 		gorseConfig:    cfg,
+		db:             db,
 	}
 }
 
@@ -98,7 +101,7 @@ func (h *GorseHandler) importAllData(ctx context.Context) (gin.H, error) {
 
 	// 导入帖子
 	var posts []model.Post
-	if err := model.DB.Find(&posts).Error; err != nil {
+	if err := h.db.Find(&posts).Error; err != nil {
 		return nil, err
 	}
 	for _, post := range posts {
@@ -126,7 +129,7 @@ func (h *GorseHandler) importAllData(ctx context.Context) (gin.H, error) {
 
 	// 导入用户
 	var users []model.User
-	if err := model.DB.Find(&users).Error; err != nil {
+	if err := h.db.Find(&users).Error; err != nil {
 		return nil, err
 	}
 	for _, user := range users {
@@ -148,7 +151,7 @@ func (h *GorseHandler) importAllData(ctx context.Context) (gin.H, error) {
 
 	// 导入点赞
 	var likes []model.PostLike
-	if err := model.DB.Find(&likes).Error; err != nil {
+	if err := h.db.Find(&likes).Error; err != nil {
 		return nil, err
 	}
 	for _, like := range likes {
@@ -167,7 +170,7 @@ func (h *GorseHandler) importAllData(ctx context.Context) (gin.H, error) {
 
 	// 导入收藏
 	var favorites []model.Favorite
-	if err := model.DB.Find(&favorites).Error; err != nil {
+	if err := h.db.Find(&favorites).Error; err != nil {
 		return nil, err
 	}
 	for _, fav := range favorites {
@@ -186,7 +189,7 @@ func (h *GorseHandler) importAllData(ctx context.Context) (gin.H, error) {
 
 	// 导入评论（按用户-帖子去重）
 	var comments []model.Comment
-	if err := model.DB.Where("status = ?", model.CommentStatusPublished).Find(&comments).Error; err != nil {
+	if err := h.db.Where("status = ?", model.CommentStatusPublished).Find(&comments).Error; err != nil {
 		return nil, err
 	}
 	seen := make(map[string]struct{})
@@ -231,4 +234,4 @@ func buildPostCategories(post *model.Post) []string {
 		categories = append(categories, "this_week")
 	}
 	return categories
-}
+}

internal/handler/group_handler.go

@@ -15,11 +15,11 @@ import (
 // GroupHandler 群组处理器
 type GroupHandler struct {
 	groupService service.GroupService
-	userService  *service.UserService
+	userService  service.UserService
 }
 
 // NewGroupHandler 创建群组处理器
-func NewGroupHandler(groupService service.GroupService, userService *service.UserService) *GroupHandler {
+func NewGroupHandler(groupService service.GroupService, userService service.UserService) *GroupHandler {
 	return &GroupHandler{
 		groupService: groupService,
 		userService:  userService,

internal/handler/message_handler.go

@@ -20,13 +20,13 @@ import (
 type MessageHandler struct {
 	chatService    service.ChatService
 	messageService *service.MessageService
-	userService    *service.UserService
+	userService    service.UserService
 	groupService   service.GroupService
 	sseHub         *sse.Hub
 }
 
 // NewMessageHandler 创建消息处理器
-func NewMessageHandler(chatService service.ChatService, messageService *service.MessageService, userService *service.UserService, groupService service.GroupService, sseHub *sse.Hub) *MessageHandler {
+func NewMessageHandler(chatService service.ChatService, messageService *service.MessageService, userService service.UserService, groupService service.GroupService, sseHub *sse.Hub) *MessageHandler {
 	return &MessageHandler{
 		chatService:    chatService,
 		messageService: messageService,

internal/handler/post_handler.go

@@ -15,12 +15,12 @@ import (
 
 // PostHandler 帖子处理器
 type PostHandler struct {
-	postService *service.PostService
-	userService *service.UserService
+	postService service.PostService
+	userService service.UserService
 }
 
 // NewPostHandler 创建帖子处理器
-func NewPostHandler(postService *service.PostService, userService *service.UserService) *PostHandler {
+func NewPostHandler(postService service.PostService, userService service.UserService) *PostHandler {
 	return &PostHandler{
 		postService: postService,
 		userService: userService,

internal/handler/system_message_handler.go

@@ -4,6 +4,7 @@ import (
 	"strconv"
 
 	"carrot_bbs/internal/cache"
+
 	"github.com/gin-gonic/gin"
 
 	"carrot_bbs/internal/dto"
@@ -16,16 +17,19 @@ import (
 type SystemMessageHandler struct {
 	systemMsgService service.SystemMessageService
 	notifyRepo       *repository.SystemNotificationRepository
+	cache            cache.Cache
 }
 
 // NewSystemMessageHandler 创建系统消息处理器
 func NewSystemMessageHandler(
 	systemMsgService service.SystemMessageService,
 	notifyRepo *repository.SystemNotificationRepository,
+	cacheBackend cache.Cache,
 ) *SystemMessageHandler {
 	return &SystemMessageHandler{
 		systemMsgService: systemMsgService,
 		notifyRepo:       notifyRepo,
+		cache:            cacheBackend,
 	}
 }
 
@@ -101,7 +105,7 @@ func (h *SystemMessageHandler) MarkAsRead(c *gin.Context) {
 		response.InternalServerError(c, "failed to mark as read")
 		return
 	}
-	cache.InvalidateUnreadSystem(cache.GetCache(), userID)
+	cache.InvalidateUnreadSystem(h.cache, userID)
 
 	response.SuccessWithMessage(c, "marked as read", nil)
 }
@@ -121,7 +125,7 @@ func (h *SystemMessageHandler) MarkAllAsRead(c *gin.Context) {
 		response.InternalServerError(c, "failed to mark all as read")
 		return
 	}
-	cache.InvalidateUnreadSystem(cache.GetCache(), userID)
+	cache.InvalidateUnreadSystem(h.cache, userID)
 
 	response.SuccessWithMessage(c, "all messages marked as read", nil)
 }
@@ -148,7 +152,7 @@ func (h *SystemMessageHandler) DeleteSystemMessage(c *gin.Context) {
 		response.InternalServerError(c, "failed to delete notification")
 		return
 	}
-	cache.InvalidateUnreadSystem(cache.GetCache(), userID)
+	cache.InvalidateUnreadSystem(h.cache, userID)
 
 	response.SuccessWithMessage(c, "notification deleted", nil)
 }

internal/handler/user_handler.go

@@ -12,12 +12,12 @@ import (
 
 // UserHandler 用户处理器
 type UserHandler struct {
-	userService *service.UserService
+	userService service.UserService
 	jwtService  *service.JWTService
 }
 
 // NewUserHandler 创建用户处理器
-func NewUserHandler(userService *service.UserService) *UserHandler {
+func NewUserHandler(userService service.UserService) *UserHandler {
 	return &UserHandler{
 		userService: userService,
 	}

internal/handler/vote_handler.go

@@ -14,11 +14,11 @@ import (
 // VoteHandler 投票处理器
 type VoteHandler struct {
 	voteService *service.VoteService
-	postService *service.PostService
+	postService service.PostService
 }
 
 // NewVoteHandler 创建投票处理器
-func NewVoteHandler(voteService *service.VoteService, postService *service.PostService) *VoteHandler {
+func NewVoteHandler(voteService *service.VoteService, postService service.PostService) *VoteHandler {
 	return &VoteHandler{
 		voteService: voteService,
 		postService: postService,