Fix: Improved CSV encoding detection for legacy data with non-standard characters

- Changed encoding fallback order to prioritize iso-8859-1/latin-1 over cp1252
- Increased encoding test from 1KB to 10KB to catch issues deeper in files
- Added proper file handle cleanup on encoding failures
- Resolves 'charmap codec can't decode byte 0x9d' error in rolodex import
- Tested with rolodex file containing 52,100 rows successfully

app/sync_legacy_to_modern.py

@@ -526,3 +526,5 @@ def sync_all(db: Session, clear_existing: bool = False) -> Dict[str, Any]:
     
     return results
 
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