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

docs/IMPORT_SYSTEM_SUMMARY.md

@@ -361,3 +361,5 @@ The implementation follows best practices:
 
 Total implementation: ~3,000 lines of production-quality code supporting 27+ table types across 35 functions.
 
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