Fix CI: bump requires-python to >=3.10

[siddhss5]

Problem

CI has been red on all PRs and on main since April 5 (#44 — "Bump dependency lower bounds to resolve Dependabot alerts"). Two separate failures stacked on top of each other:

1. Dependency resolution fails: uv sync --all-extras --dev can't resolve because the viz extra requires matplotlib>=3.8.0 but modern matplotlib versions dropped Python 3.8/3.9 support, while requires-python = ">=3.8" asks for those versions.
2. ruff not installed: even if (1) passed, uv run ruff check . couldn't spawn ruff because it wasn't in any dependency group.

Fix

Two small changes to pyproject.toml:

• Bump requires-python from ">=3.8" to ">=3.10" to match:
  • The actual CI matrix ([3.10, 3.11, 3.12] in .github/workflows/ci.yml)
  • The matplotlib constraint already imposed by the viz extra
• Add [dependency-groups].dev = ["ruff>=0.6.0"] so uv sync --dev installs ruff for the lint step.

Also added Programming Language :: Python :: 3.10/3.11/3.12 classifiers that were missing from the metadata.

Risk

Minimal. No code changes. Anyone pinned to Python 3.8/3.9 was already broken by #44 (the viz extra simply couldn't install); this PR just makes the reality explicit in the metadata.

Verified

• Local: uv sync --all-extras --dev resolves cleanly, installs ruff 0.15.x.
• Local: 307 pytest tests pass; ruff check and ruff format --check both clean.
• CI: all three Python versions (3.10/3.11/3.12) green on this PR.

Why this matters

Unblocks:

• Add Robotiq 2F-85 parallel-jaw hand; fix palm placement and MAX_APERTURE #46 (Robotiq2F85 hand class) — will go green after this merges and Add Robotiq 2F-85 parallel-jaw hand; fix palm placement and MAX_APERTURE #46 rebases onto main.
• Any future tsr PR that needs CI.