Fix clickjacking level 1 framing protection

[r1kka6]

Summary

• add a Content-Security-Policy: frame-ancestors 'none' response header to ClickjackingVulnerability LEVEL_1
• update the focused unit test so LEVEL_1 is treated as protected while the remaining vulnerable levels stay unchanged

Reproduction

Before the patch, GET /VulnerableApp/ClickjackingVulnerability/LEVEL_1 returned 200 without X-Frame-Options or Content-Security-Policy, allowing arbitrary framing.

After the patch, the same request returns Content-Security-Policy: frame-ancestors 'none'.

Verification

• docker run --rm -v "$PWD":/workspace -v "$HOME/.gradle":/root/.gradle -w /workspace eclipse-temurin:17-jdk ./gradlew test --tests org.sasanlabs.service.vulnerability.clickjacking.ClickjackingVulnerabilityTest --no-daemon
• docker run --rm -v "$PWD":/workspace -v "$HOME/.gradle":/root/.gradle -w /workspace eclipse-temurin:17-jdk ./gradlew test --no-daemon
• docker run --rm -v "$PWD":/workspace -v "$HOME/.gradle":/root/.gradle -w /workspace eclipse-temurin:17-jdk ./gradlew spotlessJavaCheck --no-daemon
• runtime check on port 9093 confirmed LEVEL_1 now returns Content-Security-Policy: frame-ancestors 'none'