chore: remove cloudflare + docker + legacy migration scripts

Phase 7 cleanup of the Vercel + Upstash consolidation plan:

- delete wrangler.toml, Dockerfile, docker-compose{,.dev}.yml,
  scripts/migrate-atlas-to-upstash.js (one-shot migration done)
- drop wrangler + mongodb devDeps and migrate* npm scripts;
  regenerate package-lock.json (-70 packages)
- prune CF/Wrangler/Atlas-export entries from .gitignore + .vercelignore
- drop MONGODB_URI from .env.deploy.example
- rewrite README for Vercel + Upstash architecture
- refresh stale Cloudflare comments in src/{logger,models,repository}

.env.deploy.example

@@ -16,7 +16,3 @@ WORKER_URL=https://store-scraper-bot.vercel.app/api/webhook
 UPSTASH_REDIS_REST_URL=
 UPSTASH_REDIS_REST_TOKEN=
 KEY_PREFIX=store-scraper-bot:
-
-# Legacy Java-bot MongoDB Atlas — required for one-shot Phase 5 migration only.
-# After successful cutover, remove this line.
-MONGODB_URI=