Drop Python 3.6-3.9 support, add Python 3.10-3.14

[Copilot]

Plan: Drop support for Python 3.6-3.9, support Python 3.10-3.14

• Update setup.py to remove Python 3.6-3.9 classifiers and add Python 3.12, 3.13, 3.14
• Update .github/workflows/ci.yml to test against Python 3.10-3.14 instead of 3.6-3.11
• Update .gitignore to exclude test artifacts
• Add explicit permissions to GitHub Actions workflow for security
• Fix black linting error in test_basic.py
• Run tests to verify changes work correctly

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[suminb]

Fix lint errors @copilot

Run black --check .
  black --check .
  # mypy --ignore-missing-imports base62.py
  shell: /usr/bin/bash -e {0}
  env:
    pythonLocation: /opt/hostedtoolcache/Python/3.11.14/x64
    PKG_CONFIG_PATH: /opt/hostedtoolcache/Python/3.11.14/x64/lib/pkgconfig
    Python_ROOT_DIR: /opt/hostedtoolcache/Python/3.11.14/x64
    Python2_ROOT_DIR: /opt/hostedtoolcache/Python/3.11.14/x64
    Python3_ROOT_DIR: /opt/hostedtoolcache/Python/3.11.14/x64
    LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.11.14/x64/lib
would reformat /home/runner/work/base62/base62/tests/test_basic.py

Oh no! 💥 💔 💥
1 file would be reformatted, 2 files would be left unchanged.
Error: Process completed with exit code 1.

[Copilot]

Fix lint errors @copilot

...

Fixed in a9d04e3. The test file had an extra blank line that black wanted to remove.