* Added date similarity support to flag_similar_records function:
* Implemented three date similarity calculation methods: linear, exponential, and threshold-based
* Added auto-detection of date columns using sophisticated heuristics
* Added handling for multiple date formats including native datetime, string representations, and timestamps
* Added configurable thresholds for date similarity calculations
* Created comprehensive tests for date auto-detection and similarity features
* Fixed duplicated parameter definitions in flag_duplicates.py