refactor: Backend modules lack type hints affecting IDE support and type safety

[kartikeyg0104]

Problem

The backend modules (qiskit_backend.py, cirq_backend.py, amazon_braket_backend.py) currently lack type annotations for function parameters and return values. This affects:

• IDE autocomplete and IntelliSense functionality
• Static type checking capabilities (mypy, pyright, etc.)
• Code readability and self-documentation
• Developer experience when working with the codebase

Current State

Affected files:

• qumat/qiskit_backend.py - 16 functions without type hints
• qumat/cirq_backend.py - 16 functions without type hints
• qumat/amazon_braket_backend.py - 16 functions without type hints

Example of current code:

def apply_hadamard_gate(circuit, qubit_index):
    circuit.h(qubit_index)