feat: add Docker/cloud environment detection to telemetry (v2.18.1)

Added isDocker and cloudPlatform fields to session_start telemetry events to enable measurement of the v2.17.1 user ID stability fix.

Changes:
- Added detectCloudPlatform() method to event-tracker.ts
- Updated trackSessionStart() to include isDocker and cloudPlatform
- Added 16 comprehensive unit tests for environment detection
- Tests for all 8 cloud platforms (Railway, Render, Fly, Heroku, AWS, K8s, GCP, Azure)
- Tests for Docker detection, local env, and combined scenarios
- Version bumped to 2.18.1
- Comprehensive CHANGELOG entry

Impact:
- Enables validation of v2.17.1 boot_id-based user ID stability
- Allows segmentation of metrics by environment
- 100% backward compatible - only adds new fields
- All tests passing, TypeScript compilation successful

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

Co-Authored-By: Claude <noreply@anthropic.com>

package.runtime.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp-runtime",
-  "version": "2.17.6",
+  "version": "2.18.1",
   "description": "n8n MCP Server Runtime Dependencies Only",
   "private": true,
   "dependencies": {