feat: initialize warpbox.dev project structure and backend

Initialize the repository with the core Go backend architecture and a frontend mockup for warpbox.dev, a self-hosted file-sharing application.

- Set up Go backend modules for configuration, HTTP server, middleware, handlers, and templates.
- Add local development scripts, environment templates, and basic project configuration.
- Include a React-based frontend mockup under the docs directory.

backend/libs/services/upload.go

@@ -0,0 +1,30 @@
+package services
+
+import (
+	"fmt"
+
+	"warpbox.dev/backend/libs/helpers"
+)
+
+type UploadService struct {
+	maxUploadSize int64
+}
+
+func NewUploadService(maxUploadSize int64) *UploadService {
+	return &UploadService{maxUploadSize: maxUploadSize}
+}
+
+func (s *UploadService) MaxUploadSize() int64 {
+	return s.maxUploadSize
+}
+
+func (s *UploadService) MaxUploadSizeLabel() string {
+	return helpers.FormatBytes(s.maxUploadSize)
+}
+
+func (s *UploadService) ValidateSize(size int64) error {
+	if size > s.maxUploadSize {
+		return fmt.Errorf("file exceeds max upload size of %s", s.MaxUploadSizeLabel())
+	}
+	return nil
+}