feat: migrate from New Relic to Prometheus/Grafana metrics

[typelets]

Changes

Removed

• ❌ New Relic APM dependencies (newrelic, @types/newrelic)
• ❌ newrelic.js configuration file
• ❌ New Relic initialization in src/server.ts
• ❌ Environment variables: NEW_RELIC_APP_NAME, NEW_RELIC_LICENSE_KEY, NEW_RELIC_LOG_LEVEL

Added

• ✅ prom-client for Prometheus metrics collection
• ✅ src/lib/prometheus.ts - Comprehensive metrics definitions
• ✅ Prometheus metrics instrumentation across all services:
  • HTTP: Request counts, duration histograms, status codes
  • WebSocket: Active connections (gauge), message counts by type and direction
  • Database: Query counts and duration by operation and table
  • Cache: Operations, hit/miss rates, operation duration
  • Code Execution: Duration and success rates by language
  • Business Events: Custom event tracking
  • Security Events: Security-related event tracking
  • System Metrics: Node.js memory, CPU, event loop, and GC metrics
• ✅ Basic Auth protection for /metrics endpoint using METRICS_API_KEY
• ✅ Grafana setup documentation in README

Modified

• 🔄 /metrics endpoint now returns Prometheus text format instead of JSON
• 🔄 /metrics endpoint now requires Basic Auth for security
• 🔄 src/lib/logger.ts - Replaced New Relic calls with Prometheus metrics
• 🔄 Updated README.md with Grafana configuration instructions

Available Metrics

All metrics are prefixed with typelets_:

• typelets_http_requests_total - Total HTTP requests (counter)
• typelets_http_request_duration_ms - HTTP request duration (histogram)
• typelets_websocket_connections_total - Active WebSocket connections (gauge)
• typelets_websocket_messages_total - WebSocket message count (counter)
• typelets_database_queries_total - Database query count (counter)
• typelets_database_query_duration_ms - Database query duration (histogram)
• typelets_cache_operations_total - Cache operations (counter)
• typelets_cache_hits_total - Cache hit/miss tracking (counter)
• typelets_code_executions_total - Code execution count (counter)
• typelets_code_execution_duration_ms - Code execution duration (histogram)
• typelets_business_events_total - Business events (counter)
• typelets_security_events_total - Security events (counter)
• Plus all default Node.js metrics (memory, CPU, event loop, GC)

Testing

• ✅ Build successful (167.1kb)
• ✅ All TypeScript errors resolved
• ✅ Metrics endpoint returns valid Prometheus format
• ✅ Basic Auth protection working correctly
• ✅ All instrumentation points verified (HTTP, WebSocket, Database, Cache, Code Execution)

[typelets]

🎉 This PR is included in version 1.9.0 🎉

The release is available on GitHub release

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