feat(audit): add comprehensive audit logging with SIEM integration

- Add AuditLog model with append-only design (timestamp, user, action, resource, IP, details, severity)
- Add audit_service.py with record/query helpers and SIEM forwarding (Syslog RFC 5424, HTTP/webhook)
- Add /api/audit-logs REST endpoints with filtering and pagination
- Add /admin/audit-logs viewer UI with real-time filters
- Add SIEM config settings (syslog, HTTP for Splunk HEC/Logstash/Grafana Loki)
- Add Alembic migration 027_add_audit_logs
- Add navigation link in admin menu
- Add comprehensive tests (20 tests covering model, service, SIEM, API, view)

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/api/__init__.py

@@ -8,6 +8,7 @@ from fastapi import APIRouter
 
 from app.api.admin_users import router as admin_users_router
 from app.api.api_tokens import router as api_tokens_router
+from app.api.audit_logs import router as audit_logs_router
 from app.api.azure import router as azure_router
 from app.api.backup import router as backup_router
 from app.api.billing import router as billing_router
@@ -82,3 +83,4 @@ router.include_router(imap_accounts_router)
 router.include_router(integrations_router)
 router.include_router(notifications_router)
 router.include_router(scheduled_jobs_router)
+router.include_router(audit_logs_router)

app/api/audit_logs.py

@@ -0,0 +1,115 @@
+"""
+Audit log REST API endpoints.
+
+Provides read-only access to the comprehensive audit log for admin users.
+Events are append-only — there are no update or delete endpoints.
+"""
+
+import logging
+from datetime import datetime
+from typing import Any
+
+from fastapi import APIRouter, Depends, Query, Request
+from sqlalchemy.orm import Session
+
+from app.auth import require_login
+from app.database import get_db
+from app.utils.audit_service import count_events, query_events
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter()
+
+
+@router.get("/audit-logs")
+@require_login
+async def list_audit_logs(
+    request: Request,
+    db: Session = Depends(get_db),
+    action: str | None = Query(None, description="Filter by action (exact match)"),
+    user: str | None = Query(None, description="Filter by username"),
+    resource_type: str | None = Query(None, description="Filter by resource type"),
+    severity: str | None = Query(None, description="Filter by severity level"),
+    since: datetime | None = Query(None, description="Only events at or after this ISO-8601 timestamp"),
+    until: datetime | None = Query(None, description="Only events at or before this ISO-8601 timestamp"),
+    limit: int = Query(50, ge=1, le=500, description="Max rows to return"),
+    offset: int = Query(0, ge=0, description="Rows to skip for pagination"),
+) -> dict[str, Any]:
+    """Return audit log entries with optional filtering and pagination.
+
+    Requires authentication. Returns events in reverse chronological order.
+    """
+    entries = query_events(
+        db,
+        action=action,
+        user=user,
+        resource_type=resource_type,
+        severity=severity,
+        since=since,
+        until=until,
+        limit=limit,
+        offset=offset,
+    )
+    total = count_events(
+        db,
+        action=action,
+        user=user,
+        resource_type=resource_type,
+        severity=severity,
+        since=since,
+        until=until,
+    )
+    return {
+        "items": [_serialize(e) for e in entries],
+        "total": total,
+        "limit": limit,
+        "offset": offset,
+    }
+
+
+@router.get("/audit-logs/actions")
+@require_login
+async def list_distinct_actions(
+    request: Request,
+    db: Session = Depends(get_db),
+) -> list[str]:
+    """Return the distinct action values present in the audit log."""
+    from app.models import AuditLog
+
+    rows = db.query(AuditLog.action).distinct().order_by(AuditLog.action).all()
+    return [r[0] for r in rows]
+
+
+@router.get("/audit-logs/users")
+@require_login
+async def list_distinct_users(
+    request: Request,
+    db: Session = Depends(get_db),
+) -> list[str]:
+    """Return the distinct user values present in the audit log."""
+    from app.models import AuditLog
+
+    rows = db.query(AuditLog.user).distinct().order_by(AuditLog.user).all()
+    return [r[0] for r in rows]
+
+
+# ------------------------------------------------------------------
+# Helpers
+# ------------------------------------------------------------------
+
+
+def _serialize(entry) -> dict[str, Any]:
+    """Convert an AuditLog row to a JSON-safe dict."""
+    import json as _json
+
+    return {
+        "id": entry.id,
+        "timestamp": entry.timestamp.isoformat() if entry.timestamp else None,
+        "user": entry.user,
+        "action": entry.action,
+        "resource_type": entry.resource_type,
+        "resource_id": entry.resource_id,
+        "ip_address": entry.ip_address,
+        "details": _json.loads(entry.details) if entry.details else None,
+        "severity": entry.severity,
+    }