feat: SEO, PWA, and performance optimizations

- Add sitemap.xml endpoint and update robots.txt for SEO - Improve
manifest.json with richer metadata and categories - Add meta tags for
social sharing and accessibility - Preload critical assets and fonts for
faster loading - Optimize login background image and resource hints -
Enhance service worker for better caching strategies - Add security
headers to server responses - Update Vite config for chunking and
dependency optimization - Add logboek.md for project tracking

static/robots.txt

@@ -1,3 +1,13 @@
-# allow crawling everything by default
+# Serengo - meet the unexpected.
 User-agent: *
-Disallow:
+Allow: /
+Disallow: /api/
+Disallow: /logout
+Disallow: /_app/
+Disallow: /.svelte-kit/
+
+# Sitemap location
+Sitemap: https://serengo.ziasvannes.tech/sitemap.xml
+
+# Crawl delay for polite crawling
+Crawl-delay: 1