fix(login): lru-cache compatibility, improve session error handling (#12099)

# Which Problems Are Solved

- Logo and heading overlap on login pages due to a -mb-4 negative margin
on the logo container
- The /login route returns a 500 when `listSessions` fails (e.g. stale
session cookies), because loadSessions has no error handling.
- The proxy logs `"fetch() returned undefined"` because
`fetchIframeOrigins` returns undefined, which lru-cache's forceFetch
treats as a fetch failure.

# How the Problems Are Solved

- Remove `-mb-4` from the logo container in DynamicTheme.
- Wrap `loadSessions` in a try/catch — failures fall through as empty
sessions instead of crashing.
- Return `null` instead of `undefined` from `fetchIframeOrigins` so
lru-cache caches it normally.

---------

Co-authored-by: Livio Spring <[email protected]>
Co-authored-by: conblem <[email protected]>

apps/login/src/components/dynamic-theme.tsx

@@ -99,7 +99,7 @@ export function DynamicTheme({
               <div className="relative mx-auto w-full max-w-[440px] px-4 py-4">
                 <Card>
                   <div className="mx-auto flex flex-col items-center space-y-8">
-                    <div className="relative -mb-4 flex flex-row items-center justify-center">
+                    <div className="relative flex flex-row items-center justify-center">
                       {branding && (
                         <Logo
                           lightSrc={branding.lightTheme?.logoUrl}

apps/login/src/components/register-form.tsx

@@ -51,7 +51,7 @@ export function RegisterForm({
     mode: "onChange",
     defaultValues: {
       email: email ?? "",
-      firstName: firstname ?? "",
+      firstname: firstname ?? "",
       lastname: lastname ?? "",
     },
   });