chore: pin peewee and polars to exact versions (#24)

Closes #24

Pins the two unpinned dependencies in requirements.txt:
- peewee (unversioned → 3.19.0)
- polars (unversioned → 1.36.1)

All other dependencies were already pinned with ==.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

requirements.txt

@@ -23,9 +23,9 @@ multidict==6.1.0
 numpy==2.1.2
 packaging==24.1
 pandas==2.2.3
-peewee
+peewee==3.19.0
 pillow==11.0.0
-polars
+polars==1.36.1
 pluggy==1.5.0
 propcache==0.2.0
 # pyarrow==17.0.0