docs(httpserver): correct tier from 4 to 3

httpserver depends on launcher (Tier 2), placing it at Tier 3.
With launcher corrected from Tier 5 to Tier 2, httpserver's tier
drops accordingly.

httpserver.go

@@ -0,0 +1,116 @@
+package httpserver
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+
+	"code.nochebuena.dev/go/launcher"
+)
+
+// Logger is the minimal interface httpserver needs — satisfied by logz.Logger.
+type Logger interface {
+	Info(msg string, args ...any)
+	Error(msg string, err error, args ...any)
+}
+
+// Config holds the HTTP server configuration.
+type Config struct {
+	Host         string        `env:"SERVER_HOST"          envDefault:"0.0.0.0"`
+	Port         int           `env:"SERVER_PORT"          envDefault:"8080"`
+	ReadTimeout  time.Duration `env:"SERVER_READ_TIMEOUT"  envDefault:"5s"`
+	WriteTimeout time.Duration `env:"SERVER_WRITE_TIMEOUT" envDefault:"10s"`
+	IdleTimeout  time.Duration `env:"SERVER_IDLE_TIMEOUT"  envDefault:"120s"`
+}
+
+// serverOpts holds functional options.
+type serverOpts struct {
+	middleware []func(http.Handler) http.Handler
+}
+
+// Option configures an httpserver component.
+type Option func(*serverOpts)
+
+// WithMiddleware applies one or more middleware to the root chi router during OnInit.
+func WithMiddleware(mw ...func(http.Handler) http.Handler) Option {
+	return func(o *serverOpts) {
+		o.middleware = append(o.middleware, mw...)
+	}
+}
+
+// HttpServerComponent is a launcher.Component that also exposes a chi.Router.
+// Embedding chi.Router gives callers the full routing API: Get, Post, Route, Mount, Use, etc.
+type HttpServerComponent interface {
+	launcher.Component
+	chi.Router
+}
+
+type httpServer struct {
+	chi.Router
+	logger Logger
+	cfg    Config
+	opts   serverOpts
+	srv    *http.Server
+}
+
+// New creates an HttpServerComponent. No middleware is installed by default;
+// use [WithMiddleware] to compose the middleware stack.
+func New(logger Logger, cfg Config, opts ...Option) HttpServerComponent {
+	o := serverOpts{}
+	for _, opt := range opts {
+		opt(&o)
+	}
+	return &httpServer{
+		Router: chi.NewRouter(),
+		logger: logger,
+		cfg:    cfg,
+		opts:   o,
+	}
+}
+
+// OnInit applies registered middleware to the router. No-op if none provided.
+func (s *httpServer) OnInit() error {
+	for _, mw := range s.opts.middleware {
+		s.Router.Use(mw)
+	}
+	return nil
+}
+
+// OnStart starts the HTTP server in a background goroutine.
+func (s *httpServer) OnStart() error {
+	host := s.cfg.Host
+	if host == "" {
+		host = "0.0.0.0"
+	}
+	port := s.cfg.Port
+	if port == 0 {
+		port = 8080
+	}
+	s.srv = &http.Server{
+		Addr:         fmt.Sprintf("%s:%d", host, port),
+		Handler:      s.Router,
+		ReadTimeout:  s.cfg.ReadTimeout,
+		WriteTimeout: s.cfg.WriteTimeout,
+		IdleTimeout:  s.cfg.IdleTimeout,
+	}
+	s.logger.Info("httpserver: starting", "addr", s.srv.Addr)
+	go func() {
+		if err := s.srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			s.logger.Error("httpserver: fatal error", err)
+		}
+	}()
+	return nil
+}
+
+// OnStop performs a graceful shutdown, waiting up to 10 seconds for in-flight
+// requests to complete.
+func (s *httpServer) OnStop() error {
+	s.logger.Info("httpserver: shutting down gracefully")
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	return s.srv.Shutdown(ctx)
+}