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/

.gitignore

@@ -0,0 +1,38 @@
+# Binaries
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with go test -c
+*.test
+
+# Output of go build
+*.out
+
+# Dependency directory
+vendor/
+
+# Go workspace file
+go.work
+go.work.sum
+
+# Environment files
+.env
+.env.*
+
+# Editor / IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# VCS files
+COMMIT.md
+RELEASE.md