Return a 404 when paring the route fails (#3860)

* return a 404 when paring the route fails

* add a playwright test for fullstack routing status codes

* Fix new playwright test

* document SSRError

* Make SSRError public and fix clippy

* Move the error display bound to the routable trait

* fix clippy

* return a more generic 404 message

* fix router tests

packages/router/src/routable.rs

@@ -592,7 +592,7 @@ type SiteMapFlattened<'a> = FlatMap<
         note = "Routable should generally be derived using the `#[derive(Routable)]` macro."
     )
 )]
-pub trait Routable: FromStr + Display + Clone + 'static {
+pub trait Routable: FromStr<Err: Display> + Display + Clone + 'static {
     /// The error that can occur when parsing a route.
     const SITE_MAP: &'static [SiteMapSegment];