VQkit v1.1 - Quantum ESPRESSO work-function workflow fix

Changes
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* Generates both VQkit_QE_WORKFUNCTION_PP.in and VQkit_QE_WORKFUNCTION_AVERAGE.in.
* Detects the QE <prefix>.save directory required by pp.x.
* Automatically runs pp.x and average.x when both executables and saved data are locally available.
* Copies avg.dat to VQkit_QE_PLANAR_POTENTIAL.dat and proceeds with work-function analysis.
* If the calculation was copied from HPC without <prefix>.save, VQkit now reports the actual missing requirement instead of repeatedly asking for a planar-average file.
* Complete HPC-ready instructions are written to VQkit_QE_WORKFUNCTION_STEPS.txt.

Validated with the VQkit test suite: 408 tests passed.
