feat(audit): Authentik events ingest worker (Phase 2 chunk 1)

Background worker that pulls Authentik's /api/v3/events/events/ on a
60s cadence and writes each event into our audit log via AuditService.
External system events now share the same /audit timeline as
internally-recorded platform mutations — operator queries don't have
to cross-reference Authentik's own UI to see logins, password changes,
group membership, impersonation, etc.

Pieces:
- src/schemas/ingest-cursor.schema.ts: one row per source, tracks
  lastEventAt + lastEventId so restarts resume without re-pulling.
- src/schemas/audit-event.schema.ts: new `externalId` field; new
  compound unique index on (source, externalId) with a partial filter
  on externalId being a string. Partial (not sparse) so internally-
  recorded events with externalId=null don't collide.
- src/audit/audit.service.ts: AuditRecordInput grows `externalId` +
  `at` fields. record() now silently swallows MongoError code 11000
  (duplicate key) so re-pulling the cursor overlap doesn't log noise.
- src/integrations/authentik.client.ts: listEvents(since, page,
  pageSize) on the existing client — reuses the admin token and base
  URL the provisioning code already configured.
- src/ingest/action-map.ts: 16 known Authentik actions → dotted
  authentik.* verbs (login, login_failed, password_changed,
  impersonation_started, …). Unknown actions fall through to
  authentik.<raw> rather than getting silently dropped.
- src/ingest/authentik.ingest.ts: OnApplicationBootstrap worker.
  Reads cursor → pulls events with created__gt=cursor, ordering=created
  ASC → paginates forward (10 pages × 100/page safety cap per tick) →
  writes each event with source='authentik' + externalId=pk + at=
  evt.created → advances cursor to the newest seen. inFlight guard
  prevents overlapping ticks. AUDIT_INGEST_ENABLED=false disables for
  test environments.
- Tenant inference: from the user's groups (same convention the portal
  flag-eval proxy uses). Admin groups stripped; first match against a
  real Tenant.slug wins. Unmatched → tenantSlug undefined, event still
  lands in the global timeline.

Smoke-tested: fresh Mongo + restart → 78 Authentik events ingested,
0 duplicates. Performed a login at app.dezky.local → next 60s tick
captured the new login row with actor email + IP. Compound unique
index on (source, externalId) verified to reject re-pulled events
silently (no error logs).

Out of scope here (covered by chunks 2 + 3):
- Stalwart webhook ingest
- OCIS file-tail ingest

services/platform-api/src/ingest/action-map.ts

@@ -0,0 +1,43 @@
+// Per-source mapping from raw event action strings to the dotted verbs we
+// store on AuditEvent.action. Known actions get a clean explicit verb; unknown
+// ones fall through to `<source>.<raw>` so we don't silently drop new event
+// types Authentik / Stalwart / OCIS introduces.
+
+import type { AuditOutcome, AuditResourceType } from '../schemas/audit-event.schema.js'
+
+export interface MappedAction {
+  action: string
+  outcome: AuditOutcome
+  resourceType?: AuditResourceType
+}
+
+// Authentik action strings (from /api/v3/events/events/ — see
+// https://goauthentik.io/docs/events/ for the full enum).
+const AUTHENTIK_MAP: Record<string, MappedAction> = {
+  login:                    { action: 'authentik.login',                   outcome: 'success', resourceType: 'user' },
+  login_failed:             { action: 'authentik.login_failed',            outcome: 'failure', resourceType: 'user' },
+  logout:                   { action: 'authentik.logout',                  outcome: 'success', resourceType: 'user' },
+  user_write:               { action: 'authentik.user_updated',            outcome: 'success', resourceType: 'user' },
+  password_set:             { action: 'authentik.password_changed',        outcome: 'success', resourceType: 'user' },
+  secret_rotate:            { action: 'authentik.secret_rotated',          outcome: 'success', resourceType: 'system' },
+  group_membership_set:     { action: 'authentik.group_membership_changed', outcome: 'success', resourceType: 'user' },
+  invitation_used:          { action: 'authentik.invitation_used',         outcome: 'success', resourceType: 'user' },
+  authorize_application:    { action: 'authentik.app_authorized',          outcome: 'success', resourceType: 'user' },
+  impersonation_started:    { action: 'authentik.impersonation_started',   outcome: 'success', resourceType: 'user' },
+  impersonation_ended:      { action: 'authentik.impersonation_ended',     outcome: 'success', resourceType: 'user' },
+  policy_execution:         { action: 'authentik.policy_executed',         outcome: 'success', resourceType: 'system' },
+  policy_exception:         { action: 'authentik.policy_exception',        outcome: 'failure', resourceType: 'system' },
+  configuration_error:      { action: 'authentik.configuration_error',     outcome: 'failure', resourceType: 'system' },
+  model_created:            { action: 'authentik.model_created',           outcome: 'success', resourceType: 'system' },
+  model_updated:            { action: 'authentik.model_updated',           outcome: 'success', resourceType: 'system' },
+  model_deleted:            { action: 'authentik.model_deleted',           outcome: 'success', resourceType: 'system' },
+}
+
+export function mapAuthentikAction(raw: string): MappedAction {
+  return (
+    AUTHENTIK_MAP[raw] ?? {
+      action: `authentik.${raw}`,
+      outcome: 'success',
+    }
+  )
+}