fix: treat set/frozenset as JSON-storable types in types_for_column_types

[KooshaPari]

Bug

types_for_column_types() mapped list, tuple, and dict to str for JSON storage, but not set or frozenset. This meant columns containing only set values would be detected as type set instead of str, which is not a valid SQLite type.

Fix

Added set and frozenset to the superclass check in types_for_column_types() so they are mapped to str, consistent with how other collection types are handled.

Testing

• Added test_types_for_column_types_set_maps_to_str to verify both set and frozenset map to str
• All 20 tests in test_utils.py pass

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📚 Documentation preview 📚: https://sqlite-utils--868.org.readthedocs.build/en/868/

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