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

db/config.ts

@@ -0,0 +1,16 @@
+import { defineDb, defineTable, column } from 'astro:db';
+
+const Guestbook = defineTable({
+  columns: {
+    id: column.number({ primaryKey: true }),
+    name: column.text(),
+    message: column.text(),
+    url: column.text({ optional: true }),
+    createdAt: column.date({ default: new Date() }),
+    approved: column.boolean({ default: false }),
+  },
+});
+
+export default defineDb({
+  tables: { Guestbook },
+});