Add MoveFileExW mock to system.h/.c

Add mock implementation for MoveFileExW Windows API function following
the existing pattern in the codebase. The mock forwards calls to the
real Windows API, allowing for future interception in the simulation
framework if needed.

src/system.c

@@ -1648,6 +1648,12 @@ BOOL mock_FindClose(HANDLE hFindFile)
     return TRUE;
 }
 
+BOOL mock_MoveFileExW(WCHAR *lpExistingFileName, WCHAR *lpNewFileName, DWORD dwFlags)
+{
+    // Forward to real MoveFileExW, last error is set by the real call
+    return MoveFileExW(lpExistingFileName, lpNewFileName, dwFlags);
+}
+
 #else
 
 int mock_clock_gettime(clockid_t clockid, struct timespec *tp)

src/system.h

@@ -73,6 +73,7 @@ int      mock__mkdir(char *path);
 HANDLE   mock_FindFirstFileA(char *lpFileName, WIN32_FIND_DATAA *lpFindFileData);
 BOOL     mock_FindNextFileA(HANDLE hFindFile, WIN32_FIND_DATAA *lpFindFileData);
 BOOL     mock_FindClose(HANDLE hFindFile);
+BOOL     mock_MoveFileExW(WCHAR *lpExistingFileName, WCHAR *lpNewFileName, DWORD dwFlags);
 #else
 int     mock_clock_gettime(clockid_t clockid, struct timespec *tp);
 int     mock_open(char *path, int flags, int mode);
@@ -124,6 +125,7 @@ int     mock_closedir(DIR *dirp);
 #define sys_FindFirstFileA   mock_FindFirstFileA
 #define sys_FindNextFileA    mock_FindNextFileA
 #define sys_FindClose        mock_FindClose
+#define sys_MoveFileExW      mock_MoveFileExW
 
 // Linux
 #define sys_mkdir            mock_mkdir
@@ -178,6 +180,7 @@ int     mock_closedir(DIR *dirp);
 #define sys_FindFirstFileA   FindFirstFileA
 #define sys_FindNextFileA    FindNextFileA
 #define sys_FindClose        FindClose
+#define sys_MoveFileExW      MoveFileExW
 
 // Linux
 #define sys_mkdir            mkdir