Three things that all blocked tunnel-start:
1. justfile: dropped set dotenv-load / set export — they pulled
.env.development into every recipe shell, where empty values
beat docker compose --env-file .env per shell-env precedence
(POSTGRES_PASSWORD was the visible casualty). Dev recipes now
pass --env-file .env.development explicitly so they're not
affected by the change.
2. canary image is distroless/static, so the wget-based healthcheck
had no binary to run and every check failed → nginx/tunnel never
started. Added cmd/healthcheck (tiny Go HTTP probe of /healthz),
built alongside canary, swapped compose healthcheck to /healthcheck.
3. Added tunnel-build and tunnel-rebuild recipes so the next person
doesn't have to remember which compose files the tunnel overlay
needs.