The production image is now a single Go binary that serves both the
JSON/WebSocket API under /api and the Svelte dashboard at /.
- New internal/webui package embeds a dist/ subdir via //go:embed.
A placeholder index.html is committed so `go build` works on a
fresh checkout; anything else in dist/ is regenerated per build
and gitignored.
- httpapi.Server.Handler mounts the embed.FS at / with SPA-style
fallback: unknown non-/api paths serve index.html so client-side
routes survive a reload. /api/* is carved out explicitly so POSTs
or typos never accidentally shadow API semantics with HTML.
- api/Dockerfile grows a node:22 builder stage that runs
`npm ci && npm run build`, and the Go stage copies ui/dist/ into
internal/webui/dist/ before `go build`. Build context moves to
the repo root (docker-compose + `make api` both updated) so the
Dockerfile can see both api/ and ui/.
With this in place, `make up` brings the whole stack online at
http://localhost:8080 — API under /api, dashboard at /. The Vite
dev server on :5173 with the /api proxy is still available via
`make ui-dev` for hot-reload development.
