refactor(server): decouple services and improve architecture

- Introduce interfaces for all major services (JWT, PostAI, Comment, Message, Notification, QRCodeLogin, Upload, Vote, etc.) to support dependency inversion.
- Move query parameters from `internal/dto` to a new `internal/query` package to separate request payloads from data transfer objects.
- Refactor `internal/router` to use embedded `RouterDeps` for cleaner dependency management.
- Decouple handlers from repositories by injecting services instead of direct repository access, ensuring proper layering.
- Improve database initialization by moving it from `internal/model` to `internal/database`.
- Optimize message decryption by implementing a more efficient `BatchDecrypt` method in `MessageEncryptor` using a worker pool.
- Enhance error handling and security by implementing fail-fast checks for encryption key length during startup.
- Clean up unused code, including the `avatar` package and several unused DTOs.

internal/handler/message_handler.go

@@ -87,14 +87,14 @@ func (h *MessageHandler) enrichConversations(ctx context.Context, convs []*model
 // MessageHandler 消息处理器
 type MessageHandler struct {
 	chatService    service.ChatService
-	messageService *service.MessageService
+	messageService service.MessageService
 	userService    service.UserService
 	groupService   service.GroupService
 	wsPublisher    ws.MessagePublisher
 }
 
 // NewMessageHandler 创建消息处理器
-func NewMessageHandler(chatService service.ChatService, messageService *service.MessageService, userService service.UserService, groupService service.GroupService, wsPublisher ws.MessagePublisher) *MessageHandler {
+func NewMessageHandler(chatService service.ChatService, messageService service.MessageService, userService service.UserService, groupService service.GroupService, wsPublisher ws.MessagePublisher) *MessageHandler {
 	return &MessageHandler{
 		chatService:    chatService,
 		messageService: messageService,