feat(launcher): initial stable release v0.9.0

Application lifecycle manager enforcing a three-phase init/wire/start sequence with reverse-order graceful shutdown and per-component stop timeouts.

What's included:
- `Component` interface (OnInit / OnStart / OnStop) and `Hook` type for BeforeStart wiring functions
- `Launcher` interface with Append, BeforeStart, Run (blocks on SIGINT/SIGTERM), and idempotent Shutdown(ctx)
- `New(logger, opts...)` constructor with configurable ComponentStopTimeout (default 15 s); no global state

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

doc.go

@@ -0,0 +1,33 @@
+// Package launcher manages the application lifecycle for Go services.
+//
+// It orchestrates a sequence of phases — init, assemble, start, wait, shutdown —
+// across a set of registered [Component] implementations. Any infrastructure piece
+// (database pool, HTTP server, background worker) that implements the three-method
+// Component interface can be managed by the launcher.
+//
+// # Lifecycle
+//
+//	OnInit  (all components, in order)   ← open connections, allocate resources
+//	BeforeStart hooks (in order)         ← wire dependencies after all inits done
+//	OnStart (all components, in order)   ← start goroutines, begin serving
+//	--- application is running ---
+//	OnStop  (all components, reverse)    ← graceful shutdown, release resources
+//
+// # Basic wiring
+//
+//	logger := logz.New(logz.Options{})
+//	lc := launcher.New(logger)
+//
+//	lc.Append(db, cache, server)
+//	lc.BeforeStart(func() error {
+//	    return server.RegisterRoutes(db, cache)
+//	})
+//
+//	if err := lc.Run(); err != nil {
+//	    logger.Error("launcher failed", err)
+//	    os.Exit(1)
+//	}
+//
+// Run blocks until SIGINT/SIGTERM is received or [Launcher.Shutdown] is called,
+// then stops all components in reverse order before returning.
+package launcher