[FXC-5449] allow varying refinements on axisymmetric body faces

[alexxu-flex]

Note

Medium Risk
Changes the meshing parameter schema and JSON translation for UniformRefinement on AxisymmetricBody, which could affect solver/mesher inputs and unit conversion behavior. Also broadens base-model preprocessing to recurse into dicts, which may impact other parameter serialization paths.

Overview
Adds optional face_spacing to UniformRefinement to allow per-face spacing overrides for AxisymmetricBody, including validation that entity names match and face indices are in range.

Updates volume meshing translation to carry these overrides through and expand them into a dense faceSpacings array for axisymmetric refinements, with new tests covering validation, translation output, and mixed-unit conversion.

Refactors Flow360BaseModel.preprocess to use a generalized _preprocess_nested helper that recursively converts dimensioned values inside both list and dict containers (replacing the prior list-only implementation).

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[benflexcompute]

This is too nested and confusing. We need to redesign the interface.

[alexxu-flex]

//User interface
face_spacing={
axisymmetric_body.segments[1] : 0.2*fl.u.cm
}
// Storage side
"face_spacing":{
("entioty_id":"$axisymmetric_body.private_attribute_id", "segment_index": 1) : {"value": 0.2, "units":"cm"}
}

[alexxu-flex]

Then you need a Pydantic model for the "segment" class.

It will be similar relationship between Windtunnel farfield and the windtunnel ghost surfaces.

class Segment(BaseModel):
    type_name:Literal["Segment"]
    entity_id:str
    segment_index: int =pd.Field(min=..., )

[cursor]

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