chore: migrate bump2version to hatch-vcs

[chrisdicaprio]

Summary

• Replace bump2version with hatch-vcs so the package version is derived from git tags at build time instead of being manually bumped in two files.
• pyproject.toml: version is now dynamic = ["version"], hatch-vcs added to build requires, [tool.hatch.version] / [tool.hatch.build.hooks.vcs] configured to write solvis/_version.py, bump2version dropped from dev deps.
• solvis/__init__.py now imports __version__ from the generated _version.py.
• Removed .bumpversion.cfg; .gitignore excludes the generated solvis/_version.py.
• uv.lock regenerated.

Test plan

• uv sync --all-extras --all-groups derives version 1.3.4.dev0+g658b5bedd.d20260715 from the v1.3.3 tag
• uv run python -c "import solvis; print(solvis.__version__)" prints the tag-derived version
• git check-ignore solvis/_version.py succeeds
• uv run pytest -q — 302 passed, 26 skipped
• uv build produces correctly-versioned wheel/sdist

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.31%. Comparing base (c520c39) to head (c086267).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #130   +/-   ##
=======================================
  Coverage   99.31%   99.31%           
=======================================
  Files          24       24           
  Lines        1318     1318           
  Branches       77       77           
=======================================
  Hits         1309     1309           
  Misses          8        8           
  Partials        1        1           

Flag	Coverage Δ
unittests	99.31% <100.00%> (ø)

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