Fail startup when the HTTP listener cannot bind (closes #167)

The HTTP server ran ListenAndServe in a goroutine, so a failed bind
was only logged and neoircd kept running without its HTTP API.

The start hook now binds the listen address and returns the bind
error, so neoircd exits 1 with an error naming the address. If serving
the bound listener later ends with anything other than a normal
shutdown, the server stops the app through fx.Shutdowner with exit
code 1; the handler tests now pass it that Shutdowner.

Tests check that a taken port fails startup, that a serve failure
stops the app with exit code 1, and that a normal stop does not. The
server tests no longer run in parallel: building the app writes the
global viper instance.

Model: opus-5-5

internal/handlers/api_test.go

@@ -325,6 +325,7 @@ func newTestServerFx(
 	cfg *config.Config,
 	mware *middleware.Middleware,
 	hdlr *handlers.Handlers,
+	shutdowner fx.Shutdowner,
 ) (*server.Server, error) {
 	srv, err := server.New(lifecycle, server.Params{ //nolint:exhaustruct
 		Logger:     log,
@@ -332,6 +333,7 @@ func newTestServerFx(
 		Config:     cfg,
 		Middleware: mware,
 		Handlers:   hdlr,
+		Shutdowner: shutdowner,
 	})
 	if err != nil {
 		return nil, fmt.Errorf("test server: %w", err)