fix: set DestroySession MaxAge to -1 instead of -1*time.Second (closes #39)

The gorilla/sessions MaxAge field expects seconds, not nanoseconds.
Previously MaxAge was set to -1000000000 (-1 * time.Second in nanoseconds),
which worked by accident since any negative value deletes the cookie.
Changed to the conventional value of -1.

internal/service/auth/auth.go

@@ -10,7 +10,6 @@ import (
 	"log/slog"
 	"net/http"
 	"strings"
-	"time"
 
 	"github.com/gorilla/sessions"
 	"go.uber.org/fx"
@@ -269,7 +268,7 @@ func (svc *Service) DestroySession(
 		return fmt.Errorf("failed to get session: %w", err)
 	}
 
-	session.Options.MaxAge = -1 * int(time.Second)
+	session.Options.MaxAge = -1
 
 	saveErr := session.Save(request, respWriter)
 	if saveErr != nil {