Stage 16: deploy infra & test contour

- backend + gateway multi-stage distroless Dockerfiles; the gateway embeds and
  serves the SPA at / and /telegram/ via go:embed (committed dist placeholder,
  real build baked in by the image's node stage)
- deploy/docker-compose.yml: backend + gateway + Postgres + Telegram connector
  (VPN sidecar) + OTel Collector + Prometheus (15d) + Tempo (72h) + Grafana,
  fronted by a caddy owning a single /_gm Basic-Auth (admin console + Grafana
  subpath); inter-service on a private network, only caddy on the edge network
- new metrics: backend accounts_created_total{kind} (robots excluded) and an
  in-memory gateway active_users{window=24h,7d} gauge
- CI: single .gitea/workflows/ci.yaml (unit/integration/ui + a gated test-contour
  deploy) on the new feature/* -> development -> master branch model; the old
  go-unit/integration/ui-test workflows are folded in; the connector-scoped
  compose is retired (superseded by deploy/)
- docs: ARCHITECTURE §11/§12/§13, root + gateway READMEs, CLAUDE.md branching,
  PLAN.md (stage 16 done + refinements + Stage 17 forward-notes)

CLAUDE.md

@@ -49,9 +49,20 @@ conversation memory — is the source of continuity. Keep it that way.
 
 ## Branching & CI
 
-- Trunk is **`master`** (owner preference). From Stage 1, work on `feature/*`
-  and merge via PR with a green CI gate. The genesis commit (Stage 0) lands on
-  `master` by necessity (an empty branch has nothing to PR into).
+- **Two long-lived branches** (Stage 16 onward): **`development`** is the
+  integration branch; **`master`** is the production trunk. Cut `feature/*`
+  branches **from `development`** and PR them back into it. (Stages 0–15 used
+  `master` as the trunk with `feature/* → master`; the genesis Stage 0 commit is
+  on `master` by necessity.)
+- A commit to a `feature/*` branch triggers **nothing**. The single workflow
+  `.gitea/workflows/ci.yaml` runs the full suite (`unit` + `integration` + `ui`)
+  on a PR into `development` or `master`, and the gated **`deploy`** job auto-rolls
+  the **test contour** on a PR into — or a push to — `development`
+  (`docker compose up -d --build` on the runner host + a `GET /` probe). A PR into
+  `master` is test-only.
+- Merge `development → master` only when CI is green; the **prod** deploy is then a
+  **manual** workflow (Stage 17), never automatic. Secrets/variables are prefixed
+  `TEST_` / `PROD_` per contour (Gitea 1.26 has no deployment environments).
 - After any push, watch the run to green before declaring a stage done — use the
   ready-made watcher, never an inline poll loop:
   `python3 ~/.claude/bin/gitea-ci-watch.py` (background). It reads `$GITEA_URL`
@@ -113,6 +124,8 @@ backend/                     # module scrabble/backend
 docs/  .gitea/workflows/  PLAN.md  CLAUDE.md  README.md
 gateway/  ui/  pkg/              # added by their stages
 platform/telegram/               # Telegram connector side-service (Stage 9): bot + gRPC API
+backend/Dockerfile gateway/Dockerfile platform/telegram/Dockerfile  # multi-stage distroless (Stage 16)
+deploy/                          # docker-compose + caddy + otelcol/prometheus/tempo/grafana (Stage 16)
 ```
 
 ## Build & test
@@ -127,9 +140,14 @@ go run ./backend/cmd/backend    # /healthz, /readyz on :8080
 
 cd ui && pnpm install && pnpm check && pnpm test:unit && pnpm build  # the UI (Stage 7+)
 pnpm start                      # UI mock mode: lobby -> game, no backend
+
+docker build -f backend/Dockerfile -t scrabble-backend .   # images (Stage 16); gateway embeds the UI
+docker build -f gateway/Dockerfile -t scrabble-gateway .
+docker compose -f deploy/docker-compose.yml config         # validate the full contour
 ```
 
-The `ui` module is a Node project (pnpm), **not** in `go.work`; its CI is
-`.gitea/workflows/ui-test.yaml`. Committed edge codegen under `ui/src/gen/`
+The `ui` module is a Node project (pnpm), **not** in `go.work`; it is the `ui` job
+of the single `.gitea/workflows/ci.yaml` (Stage 16 folded the former go-unit /
+integration / ui-test workflows into it). Committed edge codegen under `ui/src/gen/`
 (regenerate with `pnpm codegen`); pnpm build-script approval lives in
 `ui/pnpm-workspace.yaml` (`allowBuilds: esbuild: true`).