feat(#312): Implement core OpenTelemetry infrastructure

Complete the telemetry module with all acceptance criteria:

- Add service.version resource attribute from package.json
- Add deployment.environment resource attribute from env vars
- Add trace sampling configuration with OTEL_TRACES_SAMPLER_ARG
- Implement ParentBasedSampler for consistent distributed tracing
- Add comprehensive tests for SpanContextService (15 tests)
- Add comprehensive tests for LlmTelemetryDecorator (29 tests)
- Fix type safety issues (JSON.parse typing, template literals)
- Add security linter exception for package.json read

Test coverage: 74 tests passing, 85%+ coverage on telemetry module.

Fixes #312

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/.env.example

@@ -11,3 +11,18 @@ INSTANCE_URL=http://localhost:3000
 # CRITICAL: Generate a secure random key for production!
 # Generate with: node -e "console.log(require('crypto').randomBytes(32).toString('hex'))"
 ENCRYPTION_KEY=0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
+
+# OpenTelemetry Configuration
+# Enable/disable OpenTelemetry tracing (default: true)
+OTEL_ENABLED=true
+# Service name for telemetry (default: mosaic-api)
+OTEL_SERVICE_NAME=mosaic-api
+# OTLP exporter endpoint (default: http://localhost:4318/v1/traces)
+OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318/v1/traces
+# Alternative: Jaeger endpoint (legacy)
+# OTEL_EXPORTER_JAEGER_ENDPOINT=http://localhost:4318/v1/traces
+# Deployment environment (default: development, or uses NODE_ENV)
+# OTEL_DEPLOYMENT_ENVIRONMENT=production
+# Trace sampling ratio: 0.0 (none) to 1.0 (all) - default: 1.0
+# Use lower values in high-traffic production environments
+# OTEL_TRACES_SAMPLER_ARG=1.0