feat: add Nimbus Editor with Unsplash integration

- Integrated Unsplash API for image search functionality with environment configuration
- Added new Nimbus Editor page component with navigation from sidebar and mobile drawer
- Enhanced TOC with highlight animation for editor heading navigation
- Improved CDK overlay z-index hierarchy for proper menu layering
- Removed obsolete logging validation script

server/integrations/unsplash.routes.mjs

@@ -0,0 +1,45 @@
+import express from 'express';
+
+const router = express.Router();
+
+// Simple proxy to Unsplash Search API.
+// Requires UNSPLASH_ACCESS_KEY in environment; returns 501 if missing.
+router.get('/search', async (req, res) => {
+  try {
+    const ACCESS_KEY = process.env.UNSPLASH_ACCESS_KEY;
+    if (!ACCESS_KEY) {
+      return res.status(501).json({ error: 'unsplash_disabled' });
+    }
+    const q = String(req.query.q || '').trim();
+    const perPage = Math.min(50, Math.max(1, Number(req.query.perPage || 24)));
+    if (!q) return res.json({ results: [] });
+
+    const url = new URL('https://api.unsplash.com/search/photos');
+    url.searchParams.set('query', q);
+    url.searchParams.set('per_page', String(perPage));
+    url.searchParams.set('client_id', ACCESS_KEY);
+    // Prefer landscape/small for editor usage
+    url.searchParams.set('orientation', 'landscape');
+
+    const upstream = await fetch(url.toString(), { headers: { 'Accept-Version': 'v1' } });
+    if (!upstream.ok) {
+      const text = await upstream.text().catch(() => '');
+      return res.status(502).json({ error: 'unsplash_upstream_error', status: upstream.status, message: text });
+    }
+    const json = await upstream.json();
+    // Map minimal fields used by the client
+    const results = Array.isArray(json?.results) ? json.results.map((r) => ({
+      id: r.id,
+      alt_description: r.alt_description || null,
+      urls: r.urls,
+      links: r.links,
+      user: r.user ? { name: r.user.name } : undefined,
+    })) : [];
+    return res.json({ results });
+  } catch (e) {
+    console.error('[Unsplash] proxy error', e);
+    return res.status(500).json({ error: 'internal_error' });
+  }
+});
+
+export default router;