refactor: introduce service layer and migrate gRPC handlers to use it

Extract business logic from gRPC handlers into a dedicated service package.
Add context support throughout for cancellation and timeouts. Move models to
their own package, remove hardcoded credentials from config, and simplify
parsers to only handle HTML parsing.

grpc/handler_classroom.go

@@ -7,8 +7,6 @@ import (
 
 	pb "schedule_converter/proto/runner"
 
-	"schedule_converter/config"
-	"schedule_converter/parser"
 	apperr "schedule_converter/pkg/errors"
 )
 
@@ -21,31 +19,11 @@ func (h *TaskHandler) getEmptyClassrooms(ctx context.Context, payload []byte) ([
 	log := slog.With("username", req.Username, "semester", req.Semester)
 	log.Info("获取空教室任务")
 
-	httpClient, err := createHTTPClient()
+	result, err := h.service.GetEmptyClassrooms(ctx, &req)
 	if err != nil {
-		return nil, err
+		return nil, apperr.New("get_empty_classrooms", err, "获取空教室失败")
 	}
 
-	cfg := config.Get()
-	setTWFIDCookie(httpClient, cfg.BaseURL, "")
-
-	if err := executeLogin(ctx, httpClient, req.Username, req.Password); err != nil {
-		return nil, err
-	}
-
-	classrooms, err := parser.FetchEmptyClassrooms(httpClient, req.Semester, req.WeekStart, req.WeekEnd, req.CampusCode)
-	if err != nil {
-		return nil, apperr.New("fetch_empty_classrooms", err, "获取空教室失败")
-	}
-
-	pbClassrooms := convertEmptyClassrooms(classrooms)
-
-	result := &pb.EmptyClassroomResultData{
-		StudentId:  req.Username,
-		Semester:   req.Semester,
-		Classrooms: pbClassrooms,
-	}
-
-	log.Info("空教室获取成功", "classroom_count", len(pbClassrooms))
+	log.Info("空教室获取成功", "classroom_count", len(result.Classrooms))
 	return json.Marshal(result)
 }