Feat: Backend scaffolding and local dev stack

Backend/internal/httpx/response.go

@@ -0,0 +1,33 @@
+// Path: Backend/internal/httpx/response.go
+
+package httpx
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+type ErrorResponse struct {
+	Error     string `json:"error"`
+	Message   string `json:"message"`
+	RequestID string `json:"requestId,omitempty"`
+}
+
+func WriteJSON(w http.ResponseWriter, status int, payload any) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(status)
+
+	if payload == nil {
+		return
+	}
+
+	_ = json.NewEncoder(w).Encode(payload)
+}
+
+func WriteError(w http.ResponseWriter, status int, requestID, code, message string) {
+	WriteJSON(w, status, ErrorResponse{
+		Error:     code,
+		Message:   message,
+		RequestID: requestID,
+	})
+}