Fix API-key login and research navigation

Validate submitted keys against the protected research endpoint instead of the nonexistent versioned health path. Replace server-only redirects in client code with SvelteKit navigation and route successful logins to the existing new-research screen.

Align frontend research history and creation calls with the backend response contract: list items are wrapped in items and new runs return research_id.

src/routes/research/new/+page.svelte

@@ -1,5 +1,4 @@
 <script lang="ts">
-    import { redirect } from '@sveltejs/kit';
     import { isAuthenticated } from '$lib/auth';
     import { createResearch } from '$lib/sidebar';
     import { errorBanners } from '$lib/components/ErrorBannerStore';
@@ -46,7 +45,7 @@
         try {
             const result = await createResearch(key, query.trim(), language, depth);
             errorBanners.addErrorSuccess('Research wird erstellt…');
-            window.location.href = `/research/${result.id}`;
+            window.location.href = `/research/${result.research_id}`;
         } catch (e) {
             const msg = e instanceof Error ? e.message : 'Fehler beim Erstellen der Recherche.';
             error = msg;