Serve Trail at testnet.minaguard.com root

[mellowcroc]

Summary

• build the Trail frontend at the domain root
• bake testnet.minaguard.com API, GraphQL, archive, and explorer URLs
• move inner Caddy routes from /trail to root paths
• preserve the legacy /trail deploy route by stripping its prefix
• update deployment documentation

Validation

• bun install --frozen-lockfile
• bun run --filter contracts build
• production UI build with root-based testnet environment
• Caddy configuration validation
• Docker Compose configuration validation
• bash syntax and git diff checks

Deployment coordination

After the Production-gated images publish, update the Trail box local Caddyfile and outer Caddy routing together so testnet.minaguard.com switches from /trail to / without breaking the legacy hosts.