Fix mobile app submodule initialization and cleanup

- Removed incorrect swingmusic_mobile directory
- Properly initialized swingmusic_mobile submodule from swingmusic-mobile.git
- Clean submodule configuration for unified release workflow

swingmusic_mobile/windows/runner/utils.h

@@ -1,19 +0,0 @@
-#ifndef RUNNER_UTILS_H_
-#define RUNNER_UTILS_H_
-
-#include <string>
-#include <vector>
-
-// Creates a console for the process, and redirects stdout and stderr to
-// it for both the runner and the Flutter library.
-void CreateAndAttachConsole();
-
-// Takes a null-terminated wchar_t* encoded in UTF-16 and returns a std::string
-// encoded in UTF-8. Returns an empty std::string on failure.
-std::string Utf8FromUtf16(const wchar_t* utf16_string);
-
-// Gets the command line arguments passed in as a std::vector<std::string>,
-// encoded in UTF-8. Returns an empty std::vector<std::string> on failure.
-std::vector<std::string> GetCommandLineArguments();
-
-#endif  // RUNNER_UTILS_H_