fix: anchor lib/ and lib64/ patterns to repo root in .gitignore (#3083)

The unanchored `lib/` pattern matched any nested `lib/` directory, including
`src/specify_cli/bundler/lib/` added in #3070. Hatchling uses .gitignore as
its file-exclusion filter, so the bundler subpackage was silently dropped from
wheels built via `uvx --from git+...`, causing:

    ModuleNotFoundError: No module named 'specify_cli.bundler.lib'

Prefixing with `/` anchors both patterns to the repository root, which is the
intended scope (exclude top-level lib/ artefacts from old-style setuptools
installs) without affecting nested source packages.

Author: siosig