feat(cases): design independent forensic investigation and case management domain model

[SharifIbrahimDev]

Description

Closes #126

Architects and integrates a dedicated, independent Forensic Investigation & Case Management data model within the system's core database domain (\prisma/schema.prisma). This decouples long-running forensic case tracking from transient, short-lived alert incidents while supporting multi-party investigation ownership, granular audit trail history, and dynamic relational mapping to associated system incidents.

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Type of Change

• New feature (non-breaking change which adds functionality)
• Database / Architecture

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Related Issues

Closes #126

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Changes Made

1. Prisma Schema Extensions (\prisma/schema.prisma):

   • Enums:
     • \CaseStatus: \DRAFT, \ACTIVE, \IN_REVIEW, \SUSPENDED, \CLOSED, \ARCHIVED\
     • \CaseSeverity: \LOW, \MEDIUM, \HIGH, \CRITICAL\
     • \CaseAssigneeRole: \INVESTIGATOR, \LEGAL_OBSERVER, \EXTERNAL_AUDITOR\
   • Case Model: UUID primary identifier, indexed human-readable \caseNumber\ (e.g. \CASE-2026-0891), lifecycle timestamps, and relationships to assignees, incidents, activity logs, and investigation notes.
   • CaseAssignee Model: Join table supporting multi-user collaborator tracking with granular role attributes.
   • CaseIncident Model: Explicit M:N mapping table linking multiple Incident records to a single Case with \onDelete: Restrict\ relational safety.
   • CaseActivityLog Model: Audit ledger capturing state mutations, actor ID, IP address, changed fields (JSON diffs), and timestamp for tamper-evident provenance.
   • Updated Existing Models: Linked \User\ (\leadCases, \caseAssignments, \caseActivities), \Incident\ (\caseIncidents), and \InvestigationNote\ (\case).

2. Migration Script (\prisma/migrations/20260825181000_add_forensic_case_management/migration.sql):

   • Deterministic SQL DDL creating enums, tables, unique constraints, foreign keys with appropriate cascade/restrict behaviors, and indexes.

3. Domain Types (\src/domain/cases/types/index.ts):

   • Enums and TypeScript interfaces for Case domain entities, DTOs (\CreateCaseInput, \UpdateCaseInput, \AddCaseAssigneeInput, \LinkCaseIncidentInput, \LogCaseActivityInput), and audit delta structures.

4. Seed Pipeline (\src/infrastructure/database/seeds/caseSeed.ts):

   • Database seed script populating mock users, incidents, cases with various statuses/severities, multi-role assignees, linked incidents, and audit logs with JSON diffs for local development and testing.

5. Testing (\ ests/domain/cases/case-domain.test.ts):

   • Comprehensive test suite validating enum integrity, DTO structures, JSON diffs, and database seed execution.

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Testing

• 
  px prisma validate\ passes cleanly with 0 syntax errors or relation ambiguities.
• 
  px prisma generate\ generated client cleanly.
• Jest test suite passes (\ ests/domain/cases/case-domain.test.ts).
• Commitlint and lint-staged hooks passed.