Add DocMind legal risk analysis for investigation documents

[stuckvgn]

Integrate legal risk analysis patterns from DocMind into the document processing pipeline.

Purpose

After OCR and basic classification, documents need legal risk scoring:

• Is this document from an ag-gag jurisdiction? Flag for legal review before use.
• Does it contain witness-identifying information that should be redacted?
• What is the litigation risk if this document is disclosed to coalition partners?

Scope

• src/documents/legal_analyzer.py — legal risk analysis module
• Inputs: document text, jurisdiction metadata
• Outputs: risk score (low/medium/high/critical), risk factors, recommended handling
• Integrate with src/documents/ingester.py — add legal analysis step after classification
• Add risk score to evidence index database
• Dashboard: add legal risk column to evidence view

Model

Follow DocMind's pattern: parallel clause classification, plain-English explanations,
risk distribution chart. Adapt for advocacy domain:

• Ag-gag exposure (source jurisdiction)
• Witness identity exposure (names, contact details in document)
• Chain of custody gaps
• Attorney-client privilege markers

Provider

Use zero-retention or local model only — see docs/security.md §AI Provider Routing