DFTU: Use ScalapackConnector instead of direct math library calls

[lanshuyue]

This PR modifies the DFT+U module to use the ScalapackConnector class instead of direct math library function calls. The changes improve code maintainability and consistency by centralizing ScaLAPACK function calls through a unified interface.

Changes Made

1. Modified files:

   • source/source_lcao/module_dftu/dftu_hamilt.cpp
   • source/source_lcao/module_dftu/dftu_force.cpp

2. Key changes:

   • Replaced direct pzgemm_ and pdgemm_ calls with ScalapackConnector::gemm
   • Replaced direct pztranc_ calls with ScalapackConnector::tranu
   • Added proper inclusion of scalapack_connector.h header
   • Removed redundant function prototypes in dftu_force.cpp

[mohanchen]

LGTM, thanks for your contribution.