flatten monorepo, migrate off Vercel

- Remove penfield (split to own repo on Forgejo)
- Move www/ contents to root, rename to wynne.rs
- Swap @astrojs/vercel for @astrojs/node, upgrade to Astro 6
- Remove auth-astro/GitHub OAuth (TinyAuth at proxy layer)
- Remove Vercel deploy webhook
- Switch to local SQLite DB (drop Turso)
- Update generate-stats.js for new build output paths

public/stats.txt

@@ -0,0 +1,12 @@
+this site consists of [WORDS] words across [PAGES] pages
+
+there are [POSTS] blog posts
+[TXT] txt files
+and [BOOKMARKS] bookmarks
+
+[GUESTBOOK] people have signed the guestbook
+
+this file was generated automatically on deploy
+
+cheers,
+lewis