[Rbravo555]

📝 Description

Adds support for ANN-enhanced ROMs in coupled problems (fluid-thermal and thermo-mechanical).

Each coupled solver gets its own ROM basis and its own network, so the RomManager computes one SVD and trains one network per solver. This applies only to "type_of_decoder": "ann_enhanced"; coupled problems with a linear decoder keep the single monolithic basis.

The input follows the coupled_solvers layout already in master. With ANN-enhanced decoders, each coupled solver must declare its own nodal_unknowns in its ROM settings, and an error is raised if two solvers share an unknown:

"coupled_solvers": [
    {"sub_solver_name": "fluid_solver"},
    {"sub_solver_name": "thermal_solver",
     "ROM": {"model_part_name": "ThermalModelPart", "nodal_unknowns": ["TEMPERATURE"]}}
]

The basis is stored as a single RightBasisMatrix.npy, with the basis of each solver in the rows of its unknowns. The network files are prefixed with the solver name (fluid_solver_model_weights.npy, fluid_solver_SingularValues.npy, ...). The ann_enhanced_settings are shared by all the solvers.

The coupled ANN-enhanced ROM and HROM can also be run without the RomManager, as introduced in #14834.

🆕 Changelog

• Added ANN-enhanced ROMs for coupled solvers, with one basis and one network per solver
• Added HROM for coupled ANN-enhanced ROMs, with one set of weights per solver
• Added tests for the fluid-thermal and thermo-mechanical cases