chore(deps): loosen optional dependency lower bounds

[w-martin]

Problem

The optional extras in pyproject.toml pin to very recent minor versions:

[project.optional-dependencies]
pandas = ["pandas>=2.3.3"]
pandera = ["pandera>=0.29.0"]
polars = ["polars>=1.38.1"]

pandas>=2.3.3 excludes all of pandas 2.0–2.3.2. Users on corporate or conda-managed environments frequently lag 1–3 minor versions behind the latest. Unless typedframes uses an API that was specifically introduced in pandas 2.3.3, the lower bound should be relaxed to pandas>=2.0.

Investigation needed

Before changing each bound, verify whether there is a specific API, behaviour, or type stub feature from that exact version that typedframes depends on:

• pandas>=2.3.3: check src/typedframes/pandas.py for any API calls introduced in 2.3.x vs 2.0
• pandera>=0.29.0: check src/typedframes/pandera.py for any API calls introduced in 0.29.x — note that pandera renumbered after v1.0, so 0.29.0 may refer to a specific post-v1.0 release
• polars>=1.38.1: check src/typedframes/polars.py for any API calls introduced in 1.38.x vs earlier 1.x

Suggested bounds (pending verification)

[project.optional-dependencies]
pandas = ["pandas>=2.0"]
pandera = ["pandera>=0.20.0"]   # adjust based on investigation
polars = ["polars>=1.0"]         # adjust based on investigation

Add a comment in pyproject.toml if a tighter bound is intentional, e.g.:

pandas = ["pandas>=2.3.3"]  # requires DataFrame.attrs behaviour from 2.3.3