fix: extract maven-dependency-plugin property and synchronize version management docs

[SatyamPandey-07]

What kind of changes does this PR include?

• Fixes or refactors
• A new challenge
• Additional documentation
• Something else

Description

This PR addresses POM configuration consistency and documentation inaccuracies:

1. pom.xml:

   • Extracted <maven-dependency-plugin.version>3.11.0</maven-dependency-plugin.version> into <properties>, resolving the only plugin in <build><plugins> that had a hardcoded version string. This aligns with project POM conventions and allows dependency bots to track and bump it cleanly.
   • Updated the Groovy compatibility comment from (Spring Boot 4.0 manages 5.x) to (Spring Boot 4.x manages 5.x) to match the current Spring Boot 4.1.1 baseline.

2. docs/VERSION_MANAGEMENT.md:

   • Replaced references to the non-existent ./scripts/check-version-sync.sh script with the actual ./scripts/validate-versions.sh script.
   • Updated outdated 1.13.0 / 1.13.0-SNAPSHOT example release references to 1.14.0 / 1.14.0-SNAPSHOT.

3. README.md & CONTRIBUTING.md:

   • Fixed missing space before --build-arg and added build context . in the custom release Docker buildx command in README.md.
   • Corrected typos (depedencies and WrongSecretApplication) in CONTRIBUTING.md.

Relations

Closes #2661

How Has This Been Tested?

• Verified POM XML consistency and property alignment with ./mvnw validate
• Passed Spotless formatting and Tidy checks (./mvnw spotless:apply tidy:check)
• Verified ./scripts/validate-versions.sh passes successfully with zero mismatches

Checklist:

• All the contributions made are solely the work of me and my co-authors
• I used AI to generate parts of the content.
• I tested the changes in this PR (if applicable)
• I added unit tests to ensure my change works (when change in Java or on front-end code)
• I added UI tests to ensure my UI changes work (when change in the overall UI, not needed if just adding a challenge)
• The PR passes pre-commit hooks and automated tests