feat: add severity computation details

[cfabianski]

Description

Add details for severity computation to SaaS report payload

    "severity_meta": {
          "rule_severity": "low",
          "sensitive_data_categories": [
            "PII",
            "Personal Data"
          ],
          "local_data_types": false,
          "sensitive_data_category_weighting": 2,
          "rule_severity_weighting": 2,
          "final_weighting": 4,
          "display_severity": "medium"
        }

Checklist

• I've added test coverage that shows my fix or feature works as expected.
• I've updated or added documentation if required.
• I've included usage information in the description if CLI behavior was updated or added.
• PR title follows Conventional Commits format