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/empty_classroom_handler.go

@@ -4,22 +4,18 @@ import (
 	"github.com/gin-gonic/gin"
 
 	"with_you/internal/pkg/response"
-	"with_you/internal/repository"
 	"with_you/internal/service"
 )
 
 type EmptyClassroomHandler struct {
 	classroomSyncService service.EmptyClassroomSyncService
-	classroomRepo        repository.EmptyClassroomRepository
 }
 
 func NewEmptyClassroomHandler(
 	classroomSyncService service.EmptyClassroomSyncService,
-	classroomRepo repository.EmptyClassroomRepository,
 ) *EmptyClassroomHandler {
 	return &EmptyClassroomHandler{
 		classroomSyncService: classroomSyncService,
-		classroomRepo:        classroomRepo,
 	}
 }
 
@@ -77,7 +73,7 @@ func (h *EmptyClassroomHandler) ListEmptyClassrooms(c *gin.Context) {
 		return
 	}
 
-	classrooms, err := h.classroomRepo.ListByUserAndSemester(userID, semester)
+	classrooms, err := h.classroomSyncService.ListClassrooms(userID, semester)
 	if err != nil {
 		response.HandleError(c, err, "failed to list empty classrooms")
 		return