Complete Support for Quantum ESPRESSO `ibrav` Convention

[mesonepigreco]

Issue: Complete Support for Quantum ESPRESSO ibrav Convention

The code currently supports reading Quantum ESPRESSO structures from:

• pw.x input files, and
• Harmonic phonon results from DFPT (ph.x).

In Quantum ESPRESSO, high-symmetry structures can be defined using the ibrav convention (i = integer, brav = Bravais lattice).
Each ibrav value corresponds to a specific Bravais lattice type (e.g., simple cubic, bcc, hexagonal, etc.), and the lattice geometry is determined by the 6-element celldm array that uniquely defines the primitive cell.

Currently:

• Only a subset of the ibrav values is implemented in the code.
• Some of the less common ibrav options are missing.

The function responsible for converting the ibrav convention into an explicit 3×3 lattice matrix (with lattice vectors in rows) is:

def get_unit_cell_from_ibrav(ibrav, celldm)

This function is located in:
cellconstructor/Methods.py

Reference documentation for all possible ibrav values can be found in the Quantum ESPRESSO pw.x manual:

• Quantum ESPRESSO INPUT_PW documentation

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Task

• Implement all missing ibrav conventions in get_unit_cell_from_ibrav.
• Add corresponding unit tests in the test suite to verify correct parsing of each ibrav value.
• Ensure that the generated 3×3 lattice matrices match the definitions from the Quantum ESPRESSO documentation.