feat(telemetry): initial stable release v0.9.0

Single-call OTel SDK bootstrap setting all three global providers (traces → Tempo, metrics → Mimir, logs → Loki) over OTLP gRPC.

What's included:
- New(ctx, Config): bootstraps TracerProvider, MeterProvider, and LoggerProvider with OTLP gRPC exporters; sets OTel globals
- W3C TraceContext + Baggage propagation set globally
- Resource tagging: service.name, service.version, deployment.environment merged with SDK defaults
- OTLPInsecure bool for development environments without TLS
- Sequential rollback on partial initialization failure — no dangling exporters on error
- Returns shutdown func(context.Context) error; caller defers in main or wires into launcher BeforeStop
- Tier 5 module: must be imported only by application main packages; zero micro-lib dependencies

Tested-via: todo-api POC integration
Reviewed-against: docs/adr/

doc.go

@@ -0,0 +1,19 @@
+// Package telemetry bootstraps the OpenTelemetry SDK with OTLP gRPC exporters.
+//
+// It is a Tier-5 module — imported only by application main packages, never by
+// framework libraries. Micro-libs use only the OTel API (zero-overhead no-op
+// default). This module activates the real SDK with OTLP exporters so all
+// micro-libs using the OTel global API auto-instrument without importing telemetry.
+//
+// Usage:
+//
+//	shutdown, err := telemetry.New(ctx, telemetry.Config{
+//	    ServiceName:  "order-service",
+//	    OTLPEndpoint: "alloy:4317",
+//	    OTLPInsecure: true,
+//	})
+//	if err != nil {
+//	    log.Fatalf("telemetry: %v", err)
+//	}
+//	defer shutdown(ctx)
+package telemetry