refactor: migrate all page.server.ts files to typed API client

All server-side fetch calls now go through createApiClient() from
$lib/api.server.ts, which wraps openapi-fetch with the generated OpenAPI
types. This means backend changes are reflected in the frontend after
running npm run generate:api.

- Add stub src/lib/generated/api.ts (replaced by generate:api output)
- Fix GroupController: missing /api prefix and ResponseStatusException
- Root, conversations, persons, documents pages all use typed client
- Error handling uses apiError.code directly (no parseBackendError needed)
- Edit page load uses typed client; PUT action keeps raw fetch (multipart)
- Login keeps raw fetch (explicit Authorization header, not cookie auth)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/persons/+page.server.ts

@@ -1,18 +1,12 @@
-import { redirect } from '@sveltejs/kit';
-import { env } from '$env/dynamic/private';
+import { createApiClient } from '$lib/api.server';
 
 export async function load({ url, fetch }) {
     const q = url.searchParams.get('q') || '';
-    const baseUrl = env.API_INTERNAL_URL || 'http://localhost:8080';
+    const api = createApiClient(fetch);
 
-    // Query Parameter an Backend durchreichen
-    const apiUrl = new URL(`${baseUrl}/api/persons`);
-    if (q) apiUrl.searchParams.set('q', q);
+    const { data } = await api.GET('/api/persons', {
+        params: { query: { q: q || undefined } }
+    });
 
-    const res = await fetch(apiUrl.toString());
-
-    if (!res.ok) return { persons: [] };
-
-    const persons = await res.json();
-    return { persons, q };
+    return { persons: data ?? [], q };
 }

frontend/src/routes/persons/[id]/+page.server.ts

@@ -1,27 +1,23 @@
-import { error, } from '@sveltejs/kit';
-import { env } from '$env/dynamic/private';
+import { error } from '@sveltejs/kit';
+import { createApiClient } from '$lib/api.server';
+import { getErrorMessage } from '$lib/errors';
 
 export async function load({ params, fetch }) {
     const { id } = params;
-    
+    const api = createApiClient(fetch);
 
-    const baseUrl = env.API_INTERNAL_URL || 'http://localhost:8080';
+    const [personResult, docsResult] = await Promise.all([
+        api.GET('/api/persons/{id}', { params: { path: { id } } }),
+        api.GET('/api/persons/{id}/documents', { params: { path: { id } } })
+    ]);
 
-    try {
-        // Parallel Fetching: Person Infos + Ihre Dokumente
-        const [personRes, docsRes] = await Promise.all([
-            fetch(`${baseUrl}/api/persons/${id}`),
-            fetch(`${baseUrl}/api/persons/${id}/documents`)
-        ]);
-
-        if (personRes.status === 404) throw error(404, 'Person nicht gefunden');
-
-        return {
-            person: await personRes.json(),
-            documents: await docsRes.json()
-        };
-    } catch (e) {
-        if (e.status) throw e;
-        throw error(500, 'Ladefehler');
+    if (personResult.error) {
+        const code = (personResult.error as { code?: string })?.code;
+        throw error(personResult.response.status, getErrorMessage(code));
     }
+
+    return {
+        person: personResult.data,
+        documents: docsResult.data ?? []
+    };
 }