feat(deploy): optimize security, streamline build, and update antigravity UA

[tommy-ca]

Summary

This PR optimizes the deployment configuration and improves security posture.

Changes

• Security:
  • Hardened SSRF protection by disabling SECURITY_URL_ALLOWLIST_ALLOW_PRIVATE_HOSTS by default.
  • Implemented dual-network segmentation for sidecar tunnels to isolate database and cache from public-facing proxy containers.
• Deployment:
  • Replaced the redundant docker-compose-test.yml with a minimal docker-compose.build.yml override pattern.
  • Added healthchecks to Cloudflare and Tailscale sidecar services.
  • Removed hardcoded project prefixes in tunnel network configurations for better portability.
• Antigravity:
  • Updated User-Agent to 1.15.8 windows/amd64 to maintain parity with the latest official client.
• Documentation:
  • Added comprehensive guides for local rebuilding, redeploying, and accessing volume-stored configurations.