Setup Mend CLI scan

[Baraujo25]

This pull request updates the Mend (formerly WhiteSource) dependency scanning workflow to use the Mend CLI instead of the legacy Unified Agent, modernizes the setup steps, and improves compatibility with GitHub Actions. The main themes are migration to the new Mend CLI, simplification of the workflow, and updating dependencies.

Migration to Mend CLI:

• Replaces the use of the legacy WhiteSource Unified Agent with the Mend CLI for dependency scanning, including new installation and execution steps for the CLI.
• Updates environment variables and secrets to use Mend-specific credentials (MEND_USER_KEY, MEND_EMAIL) instead of the old WhiteSource API key.

Workflow and Dependency Setup Improvements:

• Updates actions/checkout and astral-sh/setup-uv to their latest versions (v6 and v7 respectively), and simplifies Python environment setup using uv venv and uv sync.
• Removes steps related to Java setup, downloading the Unified Agent, and handling external config files, as these are no longer needed with the Mend CLI.

Workflow Trigger and Logic Changes:

• Modifies the workflow trigger and adds a conditional to only run the scan on successful workflow runs or manual dispatch, improving efficiency and reducing unnecessary runs.
• Adjusts the scan step to treat