[#311] Integrate dependency-review-action into code scanning workflows

[jainlakshya]

Closes#311

Adds actions/dependency-review-action@v4 as a new workflow to the code scanning pipeline. The action scans pull requests for dependency changes and fails if any newly introduced dependency has a known vulnerability or disallowed license.

Addressing the question in the issue - what languages, builds and frameworks are supported:
The dependency-review-action is powered by the GitHub dependency graph, which supports the following ecosystems present in this repo:

• Java via Maven (pom.xml) and Gradle
• JavaScript via npm (package-lock.json)
• Python via pip and Poetry (poetry.lock)
• Rust via Cargo (Cargo.lock)
• .NET via NuGet (.csproj)
• Scala via Maven/Gradle

Configuration:

• fail-on-severity set to moderate, aligned with the existing failOnCVSS 5 threshold across other workflows
• fail-on-scopes set to runtime, consistent with existing behaviour of skipping dev dependencies
• comment-summary-in-pr set to always, surfaces scan results directly in the PR

Testing:
All workflow files validated for correct YAML syntax locally.