[Feature Request] Add CVSS4 support

**Description**
Currently, the endpoint `/security/updates/cves.json` only considers CVSS3 scores and includes only CVSS3 details in the webpage under `impact.baseMetricV3` key. Since CVSS4 is now widely adopted and UCT CVE files also contain CVSS4 scores, it would be beneficial for users to see CVSS4 scores on the CVE webpage.

**Proposed Solution**
- Extend the endpoint to include CVSS4 scores (e.g., new `impact.baseMetricV4`)
- Update the security webpage design to display CVSS4 scores alongside CVSS3 scores

**Additional Context**
CVSS4 provides more granular and up-to-date vulnerability scoring, improving risk assessment for users. Supporting it would align with industry standards.

Start at the `/security/updates/cves.json` endpoint and the security webpage code that currently exposes and displays `impact.baseMetricV3`. Trace how CVSS3 data is read from UCT CVE files, then determine the corresponding CVSS4 data path. Done means the endpoint exposes CVSS4 details and the webpage displays them alongside CVSS3.

Written by the indexing model from the issue text.