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

2025.02.28/01Ex/solve.h

@@ -0,0 +1,8 @@
+#ifndef SOLVE_H
+#define SOLVE_H
+
+#include <stddef.h>
+
+int t1_solve(char **a, int n, char *x, int (*cmp)(const char *, const char *));
+
+#endif