chore(n8n): publish under the scoped @mem0/n8n-nodes-mem0 name

The unscoped `n8n-nodes-mem0` name is already taken on npm by an
unrelated publisher, so the CD workflow could never publish it. Move to
the `@mem0` scope, matching `@mem0/pi-agent-plugin` and
`@mem0/openclaw-mem0`, and add `publishConfig.access: public` since
scoped packages default to restricted.

n8n accepts scoped community packages: it strips the scope before
enforcing the `n8n-nodes-` prefix, the same shape as n8n's own
`@n8n/n8n-nodes-langchain`. Verified end to end on n8n 2.22.6 by
installing the packed tarball into the community-packages directory and
executing a workflow against node type `@mem0/n8n-nodes-mem0.mem0`.

The directory, workflow filenames, and the `n8n-nodes-mem0-v*` tag
prefix are unchanged. pnpm-lock.yaml needs no update: the pnpm v9 root
importer is anonymous and never recorded the package name.

integrations/n8n-nodes-mem0/nodes/Mem0/Mem0.node.json

@@ -1,5 +1,5 @@
 {
-	"node": "n8n-nodes-mem0.mem0",
+	"node": "@mem0/n8n-nodes-mem0.mem0",
 	"nodeVersion": "1.0",
 	"codexVersion": "1.0",
 	"categories": ["AI"],