feat: shared links custom URL (#19999)

* feat: custom url for shared links

* feat: use a separate route and query param

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Co-authored-by: Jason Rasmussen <jason@rasm.me>

web/src/lib/managers/auth-manager.svelte.ts

@@ -6,7 +6,8 @@ import { isSharedLinkRoute } from '$lib/utils/navigation';
 import { logout } from '@immich/sdk';
 
 class AuthManager {
-  key = $derived(isSharedLinkRoute(page.route?.id) ? page.params.key : undefined);
+  isSharedLink = $derived(isSharedLinkRoute(page.route?.id));
+  params = $derived(this.isSharedLink ? { key: page.params.key, slug: page.params.slug } : {});
 
   async logout() {
     let redirectUri;