Add ZX-calculus backend

[nabe98]

Before submitting, please check the following:

• Make sure you have tests for the new code and that test passes (run pytest)
• If applicable, add a line to the [unreleased] part of CHANGELOG.md, following keep-a-changelog.
• Format added code by ruff
• Type checking by mypy and pyright
• Make sure the checks (github actions) pass.
• Check that the docs compile without errors (run make html in ./docs/ - you may need to install dependency for sphinx docs, see docs/requirements.txt.)

Then, please fill in below:

Context (if applicable):

• Add ZX-calculus backend ZXGraphState used for MBQC pattern simplification
• Refs
  • Quantum 5, 421 (2021).
  • EPTCS 384, pp. 203-219 (2023).

Description of the change:

• Implement ZXGraphState operations for local complement, pivot, Clifford removal, phase-gadget conversion, YZ-node merges, and a full_reduce pipeline, with helpers like _clifford_rules, _update_connections, and complete_graph_edges.
• Added to_zx_graphstate to convert a canonical GraphState instance into the ZXGraphState instance while preserving inputs, outputs, and measurement data
• Ship an executable example (examples/zxgraph_simplification.py) that demonstrates simplifying a random circuit’s ZX-diagram and visualizes the states before/after full_reduce
  • We used swiflow package to find the gflow. Wrapper function is implemented as gflow_wrapper.

Related issue:
close #102

[masa10-f]

@nabe98
Reminder: Please verify the functionality with a numerical test, comparing the simulated result with the circuit.

[masa10-f]

I suggest adding the include_phase_gadget parameter here.