Refactor ideal transformer stamping using MNAStampUtils

[AnasBahr]

Implement stampIdealTransformer via MNAStampUtils

Summary

This PR refactors the ideal transformer implementation by introducing and using stampIdealTransformer from MNAStampUtils across DP, EMT, and SP models.

The goal is to remove duplicated manual stamping logic and unify transformer equations in a single reusable utility.

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Changes

MNAStampUtils

• Implemented stampIdealTransformerTemplate<T>
• Supports:
  • Single-phase real
  • Single-phase complex
  • Three-phase real
• Centralized ideal transformer stamping logic

DP_Ph1_Transformer

• Replaced manual stamping with stampIdealTransformer

EMT_Ph3_Transformer

• Replaced explicit 3-phase transformer equations with utility function

SP_Ph1_Transformer

• Replaced manual transformer admittance stamping with stampIdealTransformer

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Benefits

• Removes duplicated transformer stamping code
• Improves maintainability and consistency
• Single source of truth for ideal transformer equations

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[georgii-tishenin]

Hi @AnasBahr , thanks for your PR. Some tests in Run pytest over all notebooks check are failing. Apparently, the result of ideal transformer stamping differs from what it was before. Can you investigate?