[P1-Enhancement] Add content policy and payload limits enforcement

[VirtualAgentics]

Description

Enhance data hygiene with content policy enforcement, PII scrubbing, and advanced payload limits for enterprise readiness.

Background

This enhancement extends Issue #55 (data hygiene) by adding comprehensive content policy enforcement, critical for enterprise deployments and compliance requirements.

Requirements

• Implement PII scrubbing with configurable patterns
• Add content deny-lists for blocked patterns
• Enforce max payload size limits per request
• Add max batch size limits for batch operations
• Implement content validation schemas
• Add content policy configuration
• Add content policy metrics and logging

Implementation Details

Files to modify:

• src/contextforge_memory/policy/ - New content policy module
• src/contextforge_memory/main.py - Add policy enforcement
• src/contextforge_memory/config.py - Add policy configuration
• tests/ - Add policy tests
• README.md - Document content policies

Technical approach:

• Create content policy service with configurable rules
• Implement PII detection and scrubbing
• Add deny-list pattern matching
• Enforce payload and batch size limits
• Add policy violation logging and metrics

Acceptance Criteria

• PII scrubbing works with configurable patterns
• Deny-lists block prohibited content
• Payload and batch limits are enforced
• Policy violations are logged and tracked
• Configuration is flexible and documented

Testing Requirements

• Unit tests for policy enforcement
• Integration tests for content filtering
• Performance tests for policy overhead
• Policy violation tests

Documentation Updates

• README.md - Document content policies
• Security guide - Content policy setup
• Configuration examples - Policy configuration
• Compliance guide - Enterprise requirements

Related Issues

• Extends: [P1] Implement and document data hygiene constraints #55 (data hygiene)
• Depends on: None
• Blocks: None