FINERACT-2533: Add E2E test scenarios for SavingsAccount insufficient balance withdrawal

[awaneetdecoder]

Description

Summary

This PR adds E2E test scenarios for SavingsAccount as suggested by @adamsaghy
in #5623.

Changes

SavingsAccount.feature

• Added Scenario C2441: Withdrawal fails when account has insufficient balance

SavingsAccountStepDef.java

• Added step: Client tries to withdraw {double} {string} from savings account on {string} date and expects an error
• Added step: The savings account withdrawal error response has an HTTP status of {int}
• Added step: The savings account withdrawal developer message contains {string}

Test Design Decisions

• Used try/catch FeignException pattern consistent with existing codebase
• Added Assertions.fail() inside try block to prevent false positives
• Dynamic currency via ternary operator — avoids hardcoding EUR/USD
• HTTP 403 confirmed from AbstractPlatformDomainRuleException
• Error code insufficient.account.balance confirmed from InsufficientAccountBalanceException.java

Closes

Supersedes #5623