feat: ✨ PYTHON_INJECTION_THREADSAFE env var

[remimd]

No description provided.

[Copilot]

Pull Request Overview

This PR introduces a new environment variable PYTHON_INJECTION_THREADSAFE that allows users to enable thread safety globally for the dependency injection library. The change modifies the default behavior from non-threadsafe to configurable thread safety.

Key changes:

• Added environment variable support to control global thread safety settings
• Updated the get_lock function to check the environment variable when threadsafe parameter is None
• Updated documentation to explain the new threadsafe configuration option

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.

File	Description
injection/_core/common/threading.py	Adds environment variable parsing and updates lock logic to use global threadsafe setting
README.md	Updates documentation to explain the new environment variable and threadsafe behavior

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