Upgrade mysql-connector-j from 8.4.0 to 9.3.0 across all modules

[devin-ai-integration]

Summary

Bumps com.mysql:mysql-connector-j from 8.4.0 to 9.3.0 (latest stable on Maven Central) in the four modules that declare it: core-banking-service, internet-banking-user-service, internet-banking-fund-transfer-service, internet-banking-utility-payment-service. Version is kept consistent across modules; no other changes.

Verification (JDK 21, Gradle 8.6 wrapper):

• ./gradlew build passes for user, fund-transfer, and utility-payment services (tests run against H2 and pass).
• core-banking-service: main sources build fine; its TransactionServiceTest fails to compile on main too (pre-existing FundTransferRequest constructor mismatch, unrelated to this upgrade), so tests were skipped for that module only.

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/cb6262b9adcb43c78e65777da79f8afe
Requested by: @HJscarr

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring