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/shared/infrastructure/outbox/outbox.service.ts

@@ -0,0 +1,49 @@
+import { type EventEnvelope, assertValidEnvelope  } from '@goodgo/contracts-events';
+import { Injectable, Logger } from '@nestjs/common';
+import type { Prisma } from '@prisma/client';
+// eslint-disable-next-line @typescript-eslint/consistent-type-imports -- NestJS DI requires value imports
+import { PrismaService } from '../prisma.service';
+
+/**
+ * Transactional outbox writer. Call inside the same Prisma transaction
+ * as the domain change so the row commits atomically with the state
+ * mutation it describes. The Outbox **never** publishes directly; the
+ * relay (`OutboxRelay`) tails `event_outbox` and forwards to the EventBus.
+ */
+export interface OutboxAppendOptions {
+  aggregateId?: string;
+}
+
+type EventOutboxDelegate = PrismaService['eventOutbox'];
+type PrismaTxLike = Pick<EventOutboxDelegate, 'create'> | { eventOutbox: Pick<EventOutboxDelegate, 'create'> };
+
+@Injectable()
+export class OutboxService {
+  private readonly logger = new Logger(OutboxService.name);
+
+  constructor(private readonly prisma: PrismaService) {}
+
+  async append(
+    tx: PrismaTxLike | PrismaService,
+    envelope: EventEnvelope,
+    options: OutboxAppendOptions = {},
+  ): Promise<void> {
+    assertValidEnvelope(envelope);
+    const client = ('eventOutbox' in tx ? tx.eventOutbox : tx) as EventOutboxDelegate;
+    await client.create({
+      data: {
+        eventId: envelope.eventId,
+        eventType: envelope.eventType,
+        aggregateId: options.aggregateId ?? null,
+        envelope: envelope as unknown as Prisma.InputJsonValue,
+      },
+    });
+  }
+
+  async appendStandalone(envelope: EventEnvelope, options: OutboxAppendOptions = {}): Promise<void> {
+    await this.append(this.prisma, envelope, options);
+    this.logger.warn(
+      `appendStandalone used for ${envelope.eventType} eventId=${envelope.eventId} — prefer the transactional append()`,
+    );
+  }
+}