ui: separate trackers from projects; keep header dropdown on top

- /trackers index, Trackers section on the homepage and in the header nav;
  /projects lists only projects (tracker URLs unchanged)
- header is its own z-50 layer and <main> is isolated, so maps, charts and
  sticky tables no longer paint over the nav dropdowns

src/routes/sitemap.xml/+server.ts

@@ -1,3 +1,4 @@
+import { listSummaries } from '#lib/server/lists.js';
 import { db } from '#lib/server/db/index.js';
 import { blogArticles } from '#lib/server/db/schema/index.js';
 import { SITE_ORIGIN } from '#lib/seo.js';
@@ -9,6 +10,7 @@ import type { RequestHandler } from './$types';
 const staticPaths = [
 	'/',
 	'/projects',
+	'/trackers',
 	'/blog',
 	'/lists',
 	'/projects/game-tracker',
@@ -42,7 +44,7 @@ export const GET: RequestHandler = async () => {
 			.select({ slug: blogArticles.slug, updatedAt: blogArticles.updatedAt })
 			.from(blogArticles)
 			.where(eq(blogArticles.status, 'published')),
-		db.query.lists.findMany({ columns: { slug: true } })
+		listSummaries()
 	]);
 	const entries: { path: string; lastmod?: string }[] = [
 		...staticPaths.map((path) => ({ path })),