Add PayPal debit CSV template with tests

[ydeng11]

Summary

This PR adds support for importing PayPal transaction history CSV files.

Changes

• Added PAYPAL to BankAccountPair.BankName enum - Enables PayPal as a supported bank
• Created PayPalDebitCsvTemplate - New CSV template class that:
  • Parses PayPal transaction history CSV format
  • Filters to only completed transactions (pending/denied are excluded)
  • Inverts amount signs (deposits become negative, expenses become positive) for balance tracking
  • Maps all CSV fields including Name, Type, Status, Transaction ID, etc.

Tests

Added comprehensive test suite in BankAccountCsvFactoryImplTest.PayPalDebitTests:

• parsesTransactionsCorrectly() - Verifies transaction parsing, amount inversion, and field mapping
• filtersOutPendingTransactions() - Ensures only completed transactions are processed
• invertsAmountSignsCorrectly() - Validates deposit/expense sign inversion logic

Test Data

• Added paypal_balance_debit.csv test file with sample PayPal transactions

Notes

• Amount signs are inverted to track balance where deposits reduce balance and expenses increase balance
• Only transactions with status "Completed" are processed
• Follows the same pattern as other CSV templates in the codebase