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>

libs/contracts/events/schemas/listing.approved.schema.json

@@ -0,0 +1,28 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://goodgo.vn/schemas/events/listing.approved.schema.json",
+  "title": "listing.approved",
+  "description": "Emitted when a Listing is approved by moderation and goes live.",
+  "type": "object",
+  "additionalProperties": false,
+  "required": [
+    "listingId",
+    "propertyId",
+    "agentId",
+    "approvedByUserId",
+    "approvedAt",
+    "expiresAt"
+  ],
+  "properties": {
+    "listingId": { "type": "string", "minLength": 1 },
+    "propertyId": { "type": "string", "minLength": 1 },
+    "agentId": { "type": "string", "minLength": 1 },
+    "approvedByUserId": { "type": "string", "minLength": 1 },
+    "approvedAt": { "type": "string", "format": "date-time" },
+    "expiresAt": {
+      "type": ["string", "null"],
+      "format": "date-time",
+      "description": "Null when the listing has no scheduled expiry."
+    }
+  }
+}