Rename "Sveleton Magazine" in sitemap

src/routes/sitemap/+page.svelte:28 renders <title>Sitemap — Sveleton Magazine</title> and line 31 sets the meta description to "Complete sitemap of all pages on Sveleton Magazine". The project was cut out of the Timestripe magazine and the wording stayed behind.

Tasks

• Replace the hardcoded strings with PROJECT_NAME from #lib, or use the Meta component like the other pages do
• Grep the rest of src for "Magazine" and fix any other occurrence