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

www/src/env.d.ts

@@ -1,10 +0,0 @@
-/// <reference types="astro/client" />
-
-interface ImportMetaEnv {
-  readonly VERCEL_DEPLOY_HOOK: string;
-  readonly ADMIN_GITHUB_ID: string;
-}
-
-interface ImportMeta {
-  readonly env: ImportMetaEnv;
-}