feat: SEO improvements, OG image endpoint, favicon, and metadata (#104)

- Add dynamic OG image generation endpoint (/og) adapted from monorepo
- Replace favicon with monorepo version, remove unused icon.svg
- Add seo.ts config, robots.ts, sitemap.ts for better search indexing
- Add per-page metadata (editor, viewer, settings, profile, community)
- Remove stale package-lock.json that caused ENOWORKSPACES errors with Next.js
- Add OG fonts (Geist Regular, Plus Jakarta Sans SemiBold)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -37,7 +37,7 @@
   "devDependencies": {
     "@biomejs/biome": "^2.4.2",
     "supabase": "2.75.3",
-    "turbo": "^2.8.9",
+    "turbo": "^2.8.10",
     "typescript": "5.9.2",
     "ultracite": "^7.2.3"
   },