Infer Ruff target-version from requires-python

[maresb]

Summary

Follow-up to #148. With the minimum Python now at 3.10, the Ruff target-version was a second place to keep in sync with requires-python. Ruff derives the target from project.requires-python when target-version is unset, so this PR drops the hardcoded line.

Removing it raises Ruff's inferred target from py38 to py310, which enables the pyupgrade rules already in the select list (UP006/UP035/UP045/UP007). The resulting modernization is applied in its own commit.

Commits (atomic)

1. Modernize type hints to Python 3.10+ syntax — PEP 604 unions (X | None) and PEP 585 builtin generics (list[str]), dropping the corresponding typing imports. Applied automatically via Ruff --fix --unsafe-fixes, then ruff format. 11 files, no manual edits.
2. Infer Ruff target-version from requires-python — the one-line config removal.

Splitting these keeps the mechanical churn separate from the config decision, and each commit is independently lint-clean.

Verification

• ruff check and ruff format --check pass on all tracked sources.
• mypy passes (pre-commit).
• CLI smoke test against a fresh install: labelle --version and labelle --help exit 0, and typer correctly introspects the new annotations (e.g. list[str] | None → TEXT, int | None → INTEGER). The --font and other options render as before.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR aligns Ruff’s Python targeting with the project’s declared supported Python range (3.10+) by relying on project.requires-python, and applies the resulting Ruff-driven type-hint modernizations across the codebase.

Changes:

• Modernize type annotations to Python 3.10+ syntax (PEP 604 unions, PEP 585 built-in generics) and clean up related typing imports.
• Remove the hardcoded Ruff target-version so Ruff infers it from requires-python in pyproject.toml.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/labelle/lib/utils.py	Switch typing imports/annotations to collections.abc and built-in generics.
src/labelle/lib/render_engines/horizontally_combined.py	Use collections.abc.Sequence instead of typing.Sequence.
src/labelle/lib/font_config.py	Update dict/list/optional types to Python 3.10+ syntax.
src/labelle/lib/config_file.py	Update return type to `dict[str, Any]
src/labelle/lib/barcode_writer.py	Update list type annotation to list[str].
src/labelle/lib/barcode_to_image.py	Update list/tuple/union annotations to Python 3.10+ syntax.
src/labelle/gui/q_render.py	Update optional QWidget annotation to `QWidget
src/labelle/gui/q_labels_list.py	Update Optional/List annotations to `
src/labelle/gui/q_actions.py	Update optional types to `
src/labelle/gui/gui.py	Update optional image type to `Image.Image
src/labelle/cli/cli.py	Update Typer-exposed parameter annotations to Python 3.10+ syntax and built-in generics.
pyproject.toml	Remove Ruff target-version to infer it from project.requires-python.

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