#13467 Add model padding functionality for sector model export

Add Z-direction padding support for sector models based on OPM-Flow's
padmodel.cpp. This feature enables users to add padding layers above
and/or below the exported sector model grid.

Adapts padmodel.cpp from
https://github.com/hnil/opm-flowgeomechanics/blob/geomech_hypre_cgal/examples/padmodel.cpp
Commit: 5ee483e

Fixes #13467.

ApplicationLibCode/ReservoirDataModel/SimulationFile/RigSimulationInputTool.h

@@ -31,6 +31,7 @@
 
 class RimEclipseView;
 class RimEclipseCase;
+class RigModelPaddingSettings;
 class RigSimulationInputSettings;
 class RifOpmFlowDeckFile;
 class RigSimWellData;
@@ -153,6 +154,8 @@ private:
     static std::expected<void, QString>
         exportEditNncKeyword( RimEclipseCase* eclipseCase, const RigSimulationInputSettings& settings, RifOpmFlowDeckFile& deckFile );
 
+    static std::expected<void, QString> applyModelPadding( RifOpmFlowDeckFile& deckFile, const RigModelPaddingSettings& paddingSettings );
+
     // Utility: Transform global IJK to sector-relative coordinates with refinement
     static caf::VecIjk0 transformToSectorCoordinates( const caf::VecIjk0& globalIjk, const caf::VecIjk0& min, const cvf::Vec3st& refinement );