refactor(structure): normalize folder names with leading zeros for consistency

- Renamed all folders from format NEx (e.g., 1Ex, 2Ex...) to 0NEx (01Ex, 02Ex, etc.)
- Updated subdirectories and files accordingly
- Removed old main Makefile and tasks (a01.c–a09.c, solve.c, io_status.h), likely obsolete
- Cleaned up deprecated task binaries and configs

2025.02.28/03Ex/sort.h

@@ -0,0 +1,11 @@
+#ifndef SORT_H
+#define SORT_H
+
+#include <string.h>
+
+int up_strcmp(const char *a, const char *b);
+int down_strcmp(const char *a, const char *b);
+int up_len(const char *a, const char *b);
+int down_len(const char *a, const char *b);
+
+#endif