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/__init__.py

@@ -0,0 +1,2 @@
+# Make app a package for reliable imports in tests and runtime
+