feat: Anti-Fake-Evidence System (Phase 1-4b)

Implement full evidence integrity pipeline to prevent compliance theater:
- Confidence levels (E0-E4), truth status tracking, assertion engine
- Four-Eyes approval workflow, audit trail, reject endpoint
- Evidence distribution dashboard, LLM audit routes
- Traceability matrix (backend endpoint + Compliance Hub UI tab)
- Anti-fake badges, control status machine, normative patterns
- 2 migrations, 4 test suites, MkDocs documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-compliance/compliance/api/audit_trail_utils.py

@@ -0,0 +1,53 @@
+"""Shared audit trail utilities.
+
+Extracted from isms_routes.py for reuse across evidence, control,
+and assertion routes.
+"""
+
+import hashlib
+import uuid
+from datetime import datetime
+
+from sqlalchemy.orm import Session
+
+from ..db.models import AuditTrailDB
+
+
+def generate_id() -> str:
+    """Generate a UUID string."""
+    return str(uuid.uuid4())
+
+
+def create_signature(data: str) -> str:
+    """Create SHA-256 signature."""
+    return hashlib.sha256(data.encode()).hexdigest()
+
+
+def log_audit_trail(
+    db: Session,
+    entity_type: str,
+    entity_id: str,
+    entity_name: str,
+    action: str,
+    performed_by: str,
+    field_changed: str = None,
+    old_value: str = None,
+    new_value: str = None,
+    change_summary: str = None,
+):
+    """Log an entry to the audit trail."""
+    trail = AuditTrailDB(
+        id=generate_id(),
+        entity_type=entity_type,
+        entity_id=entity_id,
+        entity_name=entity_name,
+        action=action,
+        field_changed=field_changed,
+        old_value=old_value,
+        new_value=new_value,
+        change_summary=change_summary,
+        performed_by=performed_by,
+        performed_at=datetime.utcnow(),
+        checksum=create_signature(f"{entity_type}|{entity_id}|{action}|{performed_by}"),
+    )
+    db.add(trail)