Add reactant valid-temperature range queries

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Summary

Add Fortran, C, and Python APIs for querying a database reactant’s inclusive valid temperature range in Kelvin before constructing a mixture.

Changes

• Add SpeciesThermo%get_valid_temperature_range.
• Return outer fit bounds for fitted reactants and T_ref ± 10 K for reference-only reactants.
• Add the public C API cea_reactant_get_valid_temperature_range.
• Add Python Reactant.get_valid_temperature_range().
• Handle unknown reactants and uninitialized thermo data through existing error codes.
• Add Fortran, C, and Python regression coverage.

Testing

• ctest -R cea_core_test|cea_bindc_reactant_temperature_range' -V`
• pytest source/bind/python/tests — 65 passed
• Verified touched Fortran files contain no lines over 132 characters.

Compatibility / Numerical behavior

[x] No expected changes to numerical results
[] Expected changes (explain and provide validation)