fix(integrations): address review feedback on Zapier and n8n

Zapier:
- Bound the poll budget under Zapier's step timeout and default Wait for
  Completion off; timeout message notes the add likely still succeeded
- Add offline unit tests (mocked z.request) and run them in CI
- Expose a Page input on Get Memories
- Encode memory_id in the delete path
- Update E2E to test the default no-wait path (add then search-retry)

n8n:
- Clarify the Infer description (controls extraction, not waiting)
- Add an App ID field and require at least one entity id before add
- Pass itemIndex into pollEvent errors
- Unwrap event results so wait-path output matches search and get many

integrations/zapier-mem0/package.json

@@ -22,7 +22,8 @@
   "license": "MIT",
   "main": "index.js",
   "scripts": {
-    "test": "jest --testTimeout 120000"
+    "test": "jest --testTimeout 120000",
+    "test:unit": "jest test/unit.test.js"
   },
   "engines": {
     "node": ">=18",