refactor backend packages and global db service

backend/internal/logic/notes/service.go

@@ -0,0 +1,24 @@
+package notes
+
+import (
+	"errors"
+	"strings"
+
+	"senlinai-agent/backend/internal/models"
+)
+
+type Service struct {
+}
+
+func NewService() *Service {
+	return &Service{}
+}
+
+func (s *Service) CreateNote(projectID uint, userID uint, title string, markdown string) (*models.SenlinAgentNote, error) {
+	title = strings.TrimSpace(title)
+	if title == "" {
+		return nil, errors.New("note title is required")
+	}
+	note := &models.SenlinAgentNote{ProjectID: projectID, CreatedBy: userID, Title: title, Markdown: markdown}
+	return note, models.DBService.Create(note).Error
+}