chore: update n8n to 1.115.2 and bump version to 2.18.11 (#323)

- Updated n8n to ^1.115.2 (from ^1.114.3)
- Updated n8n-core to ^1.114.0 (from ^1.113.1)
- Updated n8n-workflow to ^1.112.0 (from ^1.111.0)
- Updated @n8n/n8n-nodes-langchain to ^1.114.1 (from ^1.113.1)
- Rebuilt node database with 537 nodes (increased from 525)
- All 1,181 functional tests passing (1 flaky performance test)
- All validation tests passing
- Built and ready for deployment
- Updated README n8n version badge
- Updated CHANGELOG.md

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp",
-  "version": "2.18.10",
+  "version": "2.18.11",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
@@ -140,15 +140,15 @@
   },
   "dependencies": {
     "@modelcontextprotocol/sdk": "^1.13.2",
-    "@n8n/n8n-nodes-langchain": "^1.113.1",
+    "@n8n/n8n-nodes-langchain": "^1.114.1",
     "@supabase/supabase-js": "^2.57.4",
     "dotenv": "^16.5.0",
     "express": "^5.1.0",
     "express-rate-limit": "^7.1.5",
     "lru-cache": "^11.2.1",
-    "n8n": "^1.114.3",
-    "n8n-core": "^1.113.1",
-    "n8n-workflow": "^1.111.0",
+    "n8n": "^1.115.2",
+    "n8n-core": "^1.114.0",
+    "n8n-workflow": "^1.112.0",
     "openai": "^4.77.0",
     "sql.js": "^1.13.0",
     "uuid": "^10.0.0",