Hankan/server

server/ — not in this pass

PORT.md steps 4–6 land here: the sync API, the tutor SSE endpoint, and the Docker Compose deployment beside the Pi's existing Postgres and Caddy.

Nothing here yet, on purpose. Steps 1–3 give a fully working offline app with no server at all, and that is the version that gets used first.

What is already shaped for it:

• every syncable table carries updated_at, and seeded rows are pinned to 0 (see app/src/db/writes.ts) — the artifact's clobbering bug cannot be expressed;
• change_seq is deliberately absent: it is server-assigned and arrives with the sync layer;
• the dictionary is fetched by URL from app/src/domain/dictionary.ts, so per-band deltas can come from the Pi instead of the bundle by changing a base URL;
• the tutor goes through one Sample function (app/src/domain/stub-tutor.ts). The real endpoint implements the same contract — onText receives cumulative text, and an aborted turn stops billing — so only that file changes.

When the SSE endpoint lands, Caddy needs flush_interval -1 on the proxy or the stream buffers and the tutor appears to hang.