Adds comprehensive support for large-strain mechanical simulations by introducing templated SmallStrain and LargeStrain material models. New hyperelastic models are implemented, with corresponding interface updates across solvers, material classes, and input parsing.

Refactored core APIs to distinguish small vs. large strain via template parameters, improving extensibility and clarity.
Updated tests, CI, and input files to validate large strain mechanical problems.

• We currently have a simple Saint Venant Kirchoff model and a compressible Neo-Hookean model - $W=\frac{\mu}{2}\left(I_1-3\right)-\mu \ln J+\frac{\lambda}{2}(\ln J)^2$
• Adding a new hyperelastic model is extremely easy; One just needs $S$ and ${\partial S}/{\partial E}$ as a function of $F$ for any new model.
• In the context of homogenization, it accepts deformation gradient $\overline{F}$ as input and provides volume-averaged 1st Piola Kirchhoff stress $\overline{P}$ as output (both flattened row major format). Almost everything else from the user perspective remains unchanged.
• There are 2 new examples (tests)
  • Large strain mechanical homogenization problem with compressible Neo-Hookean model - https://github.com/DataAnalyticsEngineering/FANS/blob/develop/test/input_files/test_CompressibleNeoHookean.json
  • Large strain mechanical homogenization problem and mixed stress-strain control boundary conditions -https://github.com/DataAnalyticsEngineering/FANS/blob/develop/test/input_files/test_MixedBCs_LargeStrain.json

Checklist:

• I made sure that the CI passed before I ask for a review.
• I added a summary of the changes (compared to the last release) in the CHANGELOG.md.
• If necessary, I made changes to the documentation and/or added new content.
• I will remember to squash-and-merge, providing a useful summary of the changes of this PR.