feat: migrate backend from rust to go

This commit replaces the Axum/Rust backend with a Gin/Go implementation. The original Rust code has been archived in the 'rust' branch.

internal/utils/utils.go

@@ -0,0 +1,19 @@
+package utils
+
+import (
+	"fmt"
+	"strings"
+)
+
+func ParseDataURL(dataURL string) (string, string, error) {
+	if !strings.HasPrefix(dataURL, "data:") {
+		return "", "", fmt.Errorf("not a data URL")
+	}
+
+	parts := strings.Split(dataURL[5:], ";base64,")
+	if len(parts) != 2 {
+		return "", "", fmt.Errorf("invalid data URL format")
+	}
+
+	return parts[0], parts[1], nil
+}