refactor!: serve the static frontend trough the backend (#520)

Co-authored-by: Alessandro (Ale) Segala <43508+ItalyPaleAle@users.noreply.github.com>

backend/frontend/frontend_excluded.go

@@ -0,0 +1,9 @@
+//go:build exclude_frontend
+
+package frontend
+
+import "github.com/gin-gonic/gin"
+
+func RegisterFrontend(router *gin.Engine) error {
+	return ErrFrontendNotIncluded
+}