chore: post-v0.4.36 cleanup (delete setup.py, fix release defaults, fix README)

[vietanhdev]

Follow-up cleanup after v0.4.36 lands the CI gate and GPU publish fix. Pure cleanup — net -45 lines, no functional behaviour change for end-users.

Changes

• Delete `setup.py`. The shim that used to switch the package name to `anylabeling-gpu` is silently rejected by PEP 621 — `[project].name` in `pyproject.toml` is static. After ci: gate publish on cross-platform tests; fix GPU + resource scripts (re-target main) #232 made the GPU workflow `sed`-rewrite `pyproject.toml` directly, this file is dead code. Verified: `python -m build` produces identical metadata before and after deletion.
• `release.yml` defaults: `draft: false`, `prerelease: false`, `make_latest: 'true'`. Today every tag landed as a draft prerelease and needed a manual `gh release edit` to promote (we did this for v0.4.36). After this PR, tags publish straight away.
• `README.md`: bump "Python 3.10+" to "Python 3.11+" to match `requires-python` in `pyproject.toml`. `pip` refuses to install on 3.10 today, so the README was misleading.
• `CLAUDE.md`: the resource-script section still described the broken pre-ci: gate publish on cross-platform tests; fix GPU + resource scripts (re-target main) #232 state (`pyrcc5`/`pyrcc6` calls). Replace with the post-fix story (`pyside6-rcc` + `pyside6-lrelease` with PyQt6 import rewrite).

Verified

• Local CPU wheel build without `setup.py` produces identical `Name`, `Version`, and `Requires-Dist` metadata.
• The 9-cell test matrix on this PR will exercise both the no-setup-py install path and the unchanged unit suite.