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>

CHANGELOG.md

@@ -7,6 +7,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.37.4] - 2026-03-18
+
+### Changed
+
+- **Updated n8n dependencies**: n8n 2.11.4 → 2.12.3, n8n-core 2.11.1 → 2.12.0, n8n-workflow 2.11.1 → 2.12.0, @n8n/n8n-nodes-langchain 2.11.2 → 2.12.0
+- **Rebuilt node database**: 1,239 nodes (809 from n8n-nodes-base and @n8n/n8n-nodes-langchain, 430 community)
+
+Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en
+
 ## [2.37.3] - 2026-03-15
 
 ### Fixed