feat(integrations): add n8n community node for Mem0

A programmatic n8n community node wrapping the hosted Mem0 v3 REST API:
add, search, get, get-many, update, delete, plus usableAsTool so the n8n
AI Agent can call it.

- Zero runtime dependencies (calls REST directly), TypeScript, ESLint clean —
  meets n8n verified-node requirements
- Add supports custom_instructions, custom_categories, includes, excludes,
  a client-side entity-id guard, and async event polling (itemIndex on errors)
- Anonymous opt-out telemetry (MEM0_TELEMETRY=false)
- Docs page + docs.json/llms.txt entry, ci-gate + release wiring, AGENTS.md rows
- Verified: tsc + ESLint + live E2E (add → search → get → delete) vs api.mem0.ai

Split out of #6057 per review (separate PRs per integration).

docs/llms.txt

@@ -281,6 +281,7 @@ If the user is on a pre-current major (Python < 2, TS < 3, or Platform `output_f
 ### Developer Tools
 - [Dify](https://docs.mem0.ai/integrations/dify) [Both]: Use when the user is on Dify LLMOps.
 - [Flowise](https://docs.mem0.ai/integrations/flowise) [Both]: Use when the user is on Flowise no-code.
+- [n8n](https://docs.mem0.ai/integrations/n8n) [Both]: Use when the user builds workflows or AI agents in n8n.
 - [AgentOps](https://docs.mem0.ai/integrations/agentops) [Both]: Use when tracking agent observability with memory metadata.
 - [Respan](https://docs.mem0.ai/integrations/respan) [Both]: Use when monitoring Mem0 with Respan (formerly Keywords AI) LLM observability.
 - [Raycast](https://docs.mem0.ai/integrations/raycast) [Both]: Use when the user wants quick memory access via Raycast.