fix(routes): restore SPA routing after Echo v5 upgrade

In Echo v5, the 404 error for unmatched routes implements the
HTTPStatusCoder interface but is not a *HTTPError. This caused
the static middleware to fail to catch 404s and serve index.html
for SPA routes, leading to reloading SPA routes returning 404.

Caused by regression introduced in 9a61453e8.

Fixes #2149
Fixes #2152

pkg/routes/static.go

@@ -166,8 +166,8 @@ func static() echo.MiddlewareFunc {
 					return err
 				}
 
-				var he *echo.HTTPError
-				if !errors.As(err, &he) || he.Code != http.StatusNotFound {
+				var he echo.HTTPStatusCoder
+				if !errors.As(err, &he) || he.StatusCode() != http.StatusNotFound {
 					return err
 				}