feat: Phase 1 - Admin CMS with Links Management

Backend (updates-api):
- Add links table schema with categories, visibility, sorting
- Implement full CRUD API for links (/v1/links, /v1/admin/links)
- Create admin UI for links management (/admin/links)
- Add navigation between Updates and Links admin pages
- Add comprehensive tests for links API (7/7 passing)

Frontend (Next.js):
- Create API client for fetching links from updates-api
- Add LinksSection component with category icons
- Integrate links into homepage (between Notes and CTA)
- Add i18n entries for links section (DE/EN)
- ISR caching: 60s for links, 5min for updates

Features:
- Links organized by category (external/internal/resource/tool)
- Visibility toggle (show/hide on homepage)
- Sort order support
- Optional icons and descriptions
- Responsive grid layout (1/2/3 columns)

Testing:
- All existing tests pass
- New links API tests cover CRUD + validation
- Production build successful

Phase 1 Complete: Links management ready for deployment
Next: Phase 2 (Markdown editor + media upload)

src/lib/api-client.ts

@@ -0,0 +1,101 @@
+// API client for updates-api service
+const UPDATES_API_URL = process.env.UPDATES_API_URL || 'http://localhost:8080';
+
+export type Link = {
+  id: number;
+  title: string;
+  url: string;
+  category: 'external' | 'internal' | 'resource' | 'tool';
+  description: string | null;
+  icon: string | null;
+  sort_order: number;
+};
+
+export type Update = {
+  id: number;
+  slug: string;
+  product: 'batchmaker' | 'standalone';
+  title: string;
+  summary: string;
+  body_markdown: string;
+  published_at: string;
+  created_at: string;
+  updated_at: string;
+  link_url: string | null;
+};
+
+/**
+ * Fetch visible links from the updates-api
+ * Used for displaying links on the homepage
+ */
+export async function fetchLinks(): Promise<Link[]> {
+  try {
+    const res = await fetch(`${UPDATES_API_URL}/v1/links`, {
+      next: { revalidate: 60 }, // ISR: Cache 60s
+    });
+    
+    if (!res.ok) {
+      console.error('Failed to fetch links:', res.status, res.statusText);
+      return [];
+    }
+    
+    const data = await res.json();
+    return data.data || [];
+  } catch (error) {
+    console.error('Error fetching links:', error);
+    return [];
+  }
+}
+
+/**
+ * Fetch recent product updates
+ * @param product Filter by product (optional)
+ * @param limit Max number of updates (default: 5)
+ */
+export async function fetchUpdates(
+  product?: 'batchmaker' | 'standalone',
+  limit: number = 5
+): Promise<Update[]> {
+  try {
+    const params = new URLSearchParams();
+    if (product) params.set('product', product);
+    params.set('limit', String(limit));
+    
+    const res = await fetch(
+      `${UPDATES_API_URL}/v1/updates?${params}`,
+      { next: { revalidate: 300 } } // ISR: Cache 5min
+    );
+    
+    if (!res.ok) {
+      console.error('Failed to fetch updates:', res.status, res.statusText);
+      return [];
+    }
+    
+    const data = await res.json();
+    return data.data || [];
+  } catch (error) {
+    console.error('Error fetching updates:', error);
+    return [];
+  }
+}
+
+/**
+ * Fetch a single update by slug
+ */
+export async function fetchUpdateBySlug(slug: string): Promise<Update | null> {
+  try {
+    const res = await fetch(`${UPDATES_API_URL}/v1/updates/${slug}`, {
+      next: { revalidate: 300 },
+    });
+    
+    if (!res.ok) {
+      return null;
+    }
+    
+    const data = await res.json();
+    return data.data || null;
+  } catch (error) {
+    console.error('Error fetching update:', error);
+    return null;
+  }
+}