feat: Add IndexNow submission and sitemap updates

- Add IndexNow submit script + state tracking
- Update deploy script to notify IndexNow after healthy deploy
- Publish IndexNow verification file in public
- Update sitemaps and add env placeholders
- Pass analytics/ads/IndexNow env vars into frontend build

frontend/package.json

@@ -7,6 +7,8 @@
     "dev": "vite",
     "prebuild": "node scripts/merge-keywords.mjs && node scripts/generate-seo-assets.mjs",
     "build": "tsc --noEmit && vite build && node scripts/render-seo-shells.mjs",
+    "indexnow:submit": "node scripts/submit-indexnow.mjs",
+    "indexnow:dry-run": "node scripts/submit-indexnow.mjs --dry-run",
     "preview": "vite preview",
     "lint": "eslint .",
     "test": "vitest run",