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/helpers/json.go

@@ -0,0 +1,20 @@
+package helpers
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+type ErrorResponse struct {
+	Error string `json:"error"`
+}
+
+func WriteJSON(w http.ResponseWriter, status int, payload any) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(payload)
+}
+
+func WriteJSONError(w http.ResponseWriter, status int, message string) {
+	WriteJSON(w, status, ErrorResponse{Error: message})
+}