Switch the Fly proxy deploy strategy from `bluegreen` to `immediate` in `fly/fly.toml`. With a single proxy machine, bluegreen offers little benefit — the green machine routinely failed to reach "started" inside Fly's default 5-minute deploy timeout (the cold-start sequence of `tailscaled` → `tailscale up` → wait-for-MagicDNS → nginx startup eats most of the budget), and the failed deploys would roll back. `immediate` replaces the machine in place with a brief downtime (~5–10s) but actually completes.