Add OpenMP parallelization to BSSN RHS hot-path stencil routines

Enable OpenMP threading for the dominant computational kernels:
- makefile.inc: add -qopenmp to f90appflags
- diff_new.f90: split fderivs/fdderivs into OpenMP interior + serial boundary
- kodiss.f90: split kodis into OpenMP interior + serial boundary
- lopsidediff.f90: add OMP PARALLEL DO COLLAPSE(2) to lopsided
- fmisc.f90: parallelize symmetry_bd bulk array copy
- bssn_rhs.f90: add OMP WORKSHARE to array-syntax operations

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

AMSS_NCKU_source/lopsidediff.f90

@@ -231,12 +231,13 @@ subroutine lopsided(ex,X,Y,Z,f,f_rhs,Sfx,Sfy,Sfz,Symmetry,SoA)
 
   call symmetry_bd(3,ex,f,fh,SoA)
 
-! upper bound set ex-1 only for efficiency, 
+! upper bound set ex-1 only for efficiency,
 ! the loop body will set ex 0 also
+  !$OMP PARALLEL DO COLLAPSE(2) SCHEDULE(static) PRIVATE(i,j,k)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
-#if 0  
+#if 0
 !! old code
 ! x direction   
     if(Sfx(i,j,k) >= ZEO .and. i+3 <= imax .and. i-1 >= imin)then
@@ -482,6 +483,7 @@ subroutine lopsided(ex,X,Y,Z,f,f_rhs,Sfx,Sfy,Sfz,Symmetry,SoA)
   enddo
   enddo
   enddo
+  !$OMP END PARALLEL DO
 
   return