chore(ci): use frozen lockfile in Python CI installations

[barjin]

closes #286

[Copilot]

Pull Request Overview

This PR adds the --frozen flag to all uv sync commands in CI workflows to ensure consistent dependency installations. The change enforces that package installations must match the lockfile exactly, preventing unexpected dependency updates during CI runs.

• Adds --frozen flag to uv sync commands across all Python CI workflows
• Ensures deterministic builds by preventing lockfile modifications during CI
• Applies the change consistently to test, code check, and documentation workflows

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
.github/workflows/python-test.yaml	Added --frozen flag to 5 uv sync commands across different test job configurations
.github/workflows/python-code-checks.yaml	Added --frozen flag to 2 uv sync commands in lint and type check jobs
.github/workflows/docs.yaml	Added --frozen flag to 1 uv sync command in documentation build job

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[barjin]

Python build test running here.