feat(auth): add row/size caps + streaming to export-user-data

- Add per-collection row cap (default 10k, env EXPORT_ROW_CAP) via Prisma
  take on all findMany calls
- Add total size cap (default 100MB, env EXPORT_SIZE_CAP_MB); throws
  PayloadTooLargeException (413) when exceeded
- Convert response to Node.js Readable stream piped via NestJS StreamableFile
  to avoid large in-memory buffers
- Export ExportUserDataResult interface (stream + truncated flag) from handler
- Update controller to set Content-Type/Content-Disposition headers and
  return StreamableFile
- Document EXPORT_ROW_CAP and EXPORT_SIZE_CAP_MB env vars in Swagger
- Extend tests: row-cap assertion (take arg), size-cap 413 path, stream assertions

Fixes GOO-223 (M-1 from GOO-200 audit).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/modules/metrics/infrastructure/metrics.service.ts

@@ -10,6 +10,9 @@ import {
   HTTP_REQUESTS_TOTAL,
   GOODGO_WS_CONNECTED_CLIENTS,
   GOODGO_WS_MESSAGES_TOTAL,
+  READ_MODEL_PROJECTOR_LAG_SECONDS,
+  READ_MODEL_REFRESH_DURATION_SECONDS,
+  READ_MODEL_RECONCILIATION_DRIFT_TOTAL,
   WEB_VITALS_LCP,
   WEB_VITALS_FCP,
   WEB_VITALS_CLS,
@@ -37,6 +40,12 @@ export class MetricsService {
     private readonly wsConnectedClientsGauge: Gauge,
     @InjectMetric(GOODGO_WS_MESSAGES_TOTAL)
     private readonly wsMessagesCounter: Counter,
+    @InjectMetric(READ_MODEL_PROJECTOR_LAG_SECONDS)
+    private readonly projectorLagGauge: Gauge,
+    @InjectMetric(READ_MODEL_REFRESH_DURATION_SECONDS)
+    private readonly readModelRefreshHistogram: Histogram,
+    @InjectMetric(READ_MODEL_RECONCILIATION_DRIFT_TOTAL)
+    private readonly reconciliationDriftCounter: Counter,
     @InjectMetric(WEB_VITALS_LCP)
     private readonly lcpHistogram: Histogram,
     @InjectMetric(WEB_VITALS_FCP)
@@ -106,6 +115,21 @@ export class MetricsService {
     this.wsMessagesCounter.inc({ namespace, event, direction });
   }
 
+  /** Set current projector lag (seconds behind source stream) for a handler. */
+  setProjectorLag(handler: string, lagSeconds: number): void {
+    this.projectorLagGauge.set({ handler }, lagSeconds);
+  }
+
+  /** Record the duration of a read-model view refresh. */
+  recordReadModelRefresh(view: string, durationSeconds: number): void {
+    this.readModelRefreshHistogram.observe({ view }, durationSeconds);
+  }
+
+  /** Increment the reconciliation drift counter for a read model. */
+  recordReconciliationDrift(model: string, count = 1): void {
+    this.reconciliationDriftCounter.inc({ model }, count);
+  }
+
   /** Map metric name → the correct histogram. */
   private readonly vitalHistograms: Record<string, Histogram | undefined> = {};