fix: use semantic version comparison instead of string comparison

[gordonmurray]

Summary

• Version checks in /healthz used string comparison (lancedb_version >= "0.5") which is lexicographic, not numeric
• This produces incorrect results for certain version numbers: "0.9" >= "0.16" evaluates to True as a string, but 0.9 < 0.16 semantically
• Replaced with packaging.version.parse() which handles semver correctly
• packaging is available as a transitive dependency of pip/setuptools, no new dependencies needed

Changes

One file changed: backend/app.py

• Added from packaging.version import parse as parse_version
• Replaced two string comparisons in the compat dict with parse_version() calls

Test

from packaging.version import parse as parse_version

# String comparison (broken)
"0.9" >= "0.16"  # True (wrong)

# Semantic comparison (correct)
parse_version("0.9") >= parse_version("0.16")  # False

All currently supported versions produce correct results:

Version	schema_evolution (>= 0.5)	lance_v2_format (>= 0.16)
0.3.1	False	False
0.3.4	False	False
0.5	True	False
0.16.0	True	True
0.24.3	True	True
0.29.2	True	True

Fixes #20