chore(integrations): use pnpm, real Mem0 icon, fix Zapier field defaults

- Switch both packages from npm to pnpm (pnpm-lock.yaml) to match the
  repo convention (openclaw / pi-agent-plugin / vercel-ai-sdk); gitignore
  package-lock.json.
- Replace the placeholder n8n node icon with the real Mem0 mark (same
  asset used by integrations/mem0-plugin).
- Zapier: revert boolean/integer field defaults to strings — Zapier's
  schema requires string defaults (zapier validate now passes with 0
  errors). Runtime coercion (String(x)!=='false', Number()) is unchanged.

integrations/zapier-mem0/searches/get_memories.js

@@ -25,7 +25,7 @@ module.exports = {
 		perform,
 		inputFields: [
 			{ key: 'user_id', label: 'User ID', type: 'string', required: true },
-			{ key: 'limit', label: 'Limit', type: 'integer', default: 50 },
+			{ key: 'limit', label: 'Limit', type: 'integer', default: '50' },
 		],
 		sample: { id: '00000000-0000-0000-0000-000000000000', memory: 'User loves hiking' },
 	},

integrations/zapier-mem0/searches/search_memories.js

@@ -30,7 +30,7 @@ module.exports = {
 		inputFields: [
 			{ key: 'query', label: 'Query', type: 'string', required: true },
 			{ key: 'user_id', label: 'User ID', type: 'string', required: true },
-			{ key: 'limit', label: 'Limit', type: 'integer', default: 10 },
+			{ key: 'limit', label: 'Limit', type: 'integer', default: '10' },
 		],
 		sample: { id: '00000000-0000-0000-0000-000000000000', memory: 'User loves hiking' },
 	},