Drop support for end-of-life Python versions (3.10 first) #491

Why

Python 3.10 reached end of life in October 2026. We still declare requires-python = ">=3.10", and dependencies are starting to leave 3.10 behind:

• The filelock security fixes (4.2.1+, Dependabot alerts chore(deps): update astral-sh/setup-uv action to v8.3.2 #45-chore(deps): lock file maintenance #54) need Python 3.11+, so the 3.10 fork of uv.lock is stuck at filelock 4.1.0. filelock is dev-only (tox, virtualenv), but the alerts can't be closed while 3.10 is in the lock.
• zensical 0.1 needs 3.11+, so the docs group carries a python_version >= '3.11' marker (chore(deps): refresh dependencies; zensical 0.1, Node 26 for the Renovate validator #490).
• uv lock keeps a separate < 3.11 fork for several packages (cachetools, platformdirs, pyproject-api, tox, ...), so 3.10 gets older versions than every other interpreter.

Proposed policy

Drop a Python version in the first minor release after its end-of-life date, with a runtime warning in the release line before it (the same rule as any breaking change). State the policy in the docs so future drops (3.11 in October 2027) follow it without a new discussion.

Plan

0.5.x (warn first)

• On import under Python 3.10, emit a FutureWarning (visible by default, unlike DeprecationWarning) saying 0.6.0 requires Python 3.11+. Add a test, and make sure filterwarnings = ["error"] does not break the 3.10 CI job.
• Changelog fragment (deprecation).

Done in #493. It ships in the next 0.5.x release, which has to be cut before the first 0.6.0 change below is merged: release.yml releases only from master.

0.6.0 (drop)

• pyproject.toml: requires-python = ">=3.11", drop the 3.10 classifier, mypy python_version = "3.11", and remove the zensical marker.
• Remove the import-time warning (_warn_python_310 in fastapi_cachex/__init__.py, its filterwarnings entry in pyproject.toml, and tests/test_python_support.py).
• CI: drop 3.10 from the test.yml matrix. lowest.yml and tox -e lowest run on 3.11 (tox.ini env_list, base_python, gh-actions map). Recheck the lowest dependency floors on 3.11.
• Code: let ruff's pyupgrade rules remove 3.10-only shims, such as typing_extensions imports that are stdlib in 3.11 and sys.version_info branches.
• Docs, in English and zh-TW: MIGRATING_FROM_FASTAPI_CACHE2.md, COMPARISON.md, DEVELOPMENT.md (tox section, Zensical note) and CLAUDE.md.
• Add docs/MIGRATING_0_6.md with a zh-TW copy and nav entries, containing a "Python 3.11 or later" section. (feat: warn on import under Python 3.10, which 0.6.0 drops #493). In 0.6.0, reword it from "will require" to "requires", but keep the silencing recipes and the #python-311 anchor: the 0.5.x warning links to en/stable/MIGRATING_0_6/#python-311, and once 0.6.0 is out, stable serves the 0.6.0 page to everyone still on 0.5.x and Python 3.10.
• Write down the support policy above, for example in SECURITY.md or the README.
• Changelog fragment (removal).