chore: update n8n to 2.12.3 and bump version to 2.37.4

- Updated n8n from 2.11.4 to 2.12.3
- Updated n8n-core from 2.11.1 to 2.12.0
- Updated n8n-workflow from 2.11.1 to 2.12.0
- Updated @n8n/n8n-nodes-langchain from 2.11.2 to 2.12.0
- Rebuilt node database with 1,239 nodes (809 core + 430 community)
- Updated README badge with new n8n version
- Updated CHANGELOG with dependency changes

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

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

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp",
-  "version": "2.37.3",
+  "version": "2.37.4",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
@@ -153,16 +153,16 @@
   },
   "dependencies": {
     "@modelcontextprotocol/sdk": "^1.27.1",
-    "@n8n/n8n-nodes-langchain": "^2.11.2",
+    "@n8n/n8n-nodes-langchain": "^2.12.0",
     "@supabase/supabase-js": "^2.57.4",
     "dotenv": "^16.5.0",
     "express": "^5.1.0",
     "express-rate-limit": "^7.1.5",
     "form-data": "^4.0.5",
     "lru-cache": "^11.2.1",
-    "n8n": "^2.11.4",
-    "n8n-core": "^2.11.1",
-    "n8n-workflow": "^2.11.1",
+    "n8n": "^2.12.3",
+    "n8n-core": "^2.12.0",
+    "n8n-workflow": "^2.12.0",
     "openai": "^4.77.0",
     "sql.js": "^1.13.0",
     "tslib": "^2.6.2",