chore: bump version to 2.7.23 and update documentation

- Bump version from 2.7.22 to 2.7.23 in package.json
- Update version badge in README.md
- Add tests badge showing 1,182 passing tests
- Add comprehensive CHANGELOG entry for v2.7.23 documenting:
  - Complete testing infrastructure implementation
  - 933 unit tests and 249 integration tests
  - All CI test failures fixed
  - Test architecture enhancements
  - Documentation updates
  - Development artifact cleanup

🤖 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": "2.7.22",
+  "version": "2.7.23",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "bin": {