fix: DataFrame mapping and datetime parsing

[mdqst]

Description switched df.map(...) to df.applymap(...) - DataFrames don’t have map, so the old code would crash. also removed format='mixed' in pd.to_datetime(...) because Pandas doesn’t support it. dates in different formats now parse smoothly with errors='coerce'.

Tests ran the script on sample data; all transformations and datetime parsing work without errors.

Additional context this fixes crashes when processing DataFrames with mixed date formats or when trying to apply element-wise transformations using map.

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