Add risk scoring for discovered PII

[jzonthemtn]

Summary

Phinder reports entity counts per file/bucket but does not assign aggregate risk scores. A file with 500 SSNs is treated the same as a file with 2 first names in the report output.

Proposal

Add risk scoring:

• Assign severity weights per entity type (SSN > first name)
• Calculate aggregate risk scores per file, bucket, or data source
• Support custom severity configurations
• Sort and filter reports by risk score to prioritize remediation

Acceptance Criteria

• Phinder assigns a risk score to each discovered PII location based on entity type sensitivity, volume, and exposure context
• Risk scores are configurable (weighting per entity type)
• Scan results sortable/filterable by risk score
• Tests cover risk scoring with varied entity types and volumes
• Documentation describes the scoring methodology and configuration