feature: upgrade Spring Boot framework 3.3.3 -> 3.5.15

[devin-ai-integration]

Summary

Upgrades the Spring Boot framework from 3.3.3 to the latest stable 3.5.15 (current 3.x line) to pick up dependency, security, and bugfix updates. The app remains on Java 17, which Spring Boot 3.5 supports, so this is a single-line, in-major upgrade.

 <artifactId>spring-boot-starter-parent</artifactId>
-<version>3.3.3</version>
+<version>3.5.15</version>

No source changes were required — the upgrade is transparent to the application code (JPA/jakarta.*, Spring Security 6, Thymeleaf all carry forward).

Verification

• ./mvnw clean test — passes (BankappApplicationTests contextLoads, 1/1) against a live MySQL 8.
• ./mvnw clean package — builds the executable jar successfully.

Notes

• A pre-existing Hibernate warning surfaces (MySQL8Dialect deprecated; use MySQLDialect) — unrelated to this upgrade and left untouched to keep the change minimal.
• CI for this repo is Jenkins (Jenkinsfile); there are no GitHub Actions workflows.

Link to Devin session: https://app.devin.ai/sessions/451eae28daaf455091e39935c89b2319
Requested by: @louisgenest-devindemo

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[devin-ai-integration]

✅ Runtime test results — Spring Boot 3.5.15 upgrade

Ran the upgraded app locally on this branch (./mvnw spring-boot:run) against MySQL 8 and exercised the full banking flow through the browser UI. All assertions passed.

Test	Result
App boots on Spring Boot 3.5.15, serves /login	✅
Register 2 users → redirect to /login	✅
Login (Spring Security 6 form login) → dashboard, balance $0.00	✅
Deposit $100 → $0.00 → $100.00	✅
Withdraw $30 → $100.00 → $70.00	✅
Transfer $20 to bob → alice $50.00	✅
Transactions page lists all 3 ops	✅
Recipient bob credited → $20.00	✅
Adversarial: withdraw $999 → "Insufficient funds", balance unchanged	✅

Also ./mvnw clean test (1/1) and ./mvnw clean package succeed on the branch.

Core flow — balances update correctly

Deposit → $100.00	Withdraw → $70.00	Transfer → $50.00

Transactions history	Recipient credited $20	Adversarial: Insufficient funds

Notes

• Pre-existing Hibernate warning MySQL8Dialect deprecated; use MySQLDialect also appears on the new version — unrelated to this upgrade, left untouched.
• Repo CI is Jenkins (Jenkinsfile), no GitHub Actions. PR-level Snyk security + license checks are green.
• Upgrade targets latest stable 3.x (3.5.15), not Spring Boot 4.x (a larger major migration).

Tested by Devin — session: https://app.devin.ai/sessions/451eae28daaf455091e39935c89b2319