refactor: migrate UptimeRobot configuration from client-side dynamic form to environment variable-based monitoring

refactor: enhance Cloudflare outbound proxy with improved request patching, robust header handling, and secure environment configuration.

feat: extend cloudflare-proxy to support fetch interception and simplify configuration, while removing redundant dns-fix utility.

feat: enhance Cloudflare proxy with shared secret support, add uptime monitoring features, and improve startup timeout handling

refactor: standardize Cloudflare proxy implementation, clean up configuration, and update documentation

feat: rename proxy files and make CLOUDFLARE_PROXY_URL required