build: Docker setup (compose: postgres + all-in-one api image)

- Dockerfile: 3-stage — Flutter web build, NestJS build, slim node runtime.
  Runtime copies dist + node_modules + prisma + the web bundle
  (WEB_CLIENT_DIR=/app/web), runs `prisma migrate deploy` then `node
  dist/main.js`. One container serves client + API on :3000.
- docker-compose.yml: postgres:16-alpine with a healthcheck + the api
  service; config from backend/.env (Compose v2 strips quotes),
  DATABASE_URL + GOOGLE_APPLICATION_CREDENTIALS overridden for the
  container, serviceAccount.json bind-mounted read-only.
- .dockerignore keeps node_modules/build/secrets out of the context.

Not run here (no Docker on this box); the stack also runs natively against
the local Postgres.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,34 @@
+# syntax=docker/dockerfile:1
+
+# --- 1. Flutter web build -------------------------------------------------
+FROM ghcr.io/cirruslabs/flutter:stable AS web
+WORKDIR /src
+COPY client/app/pubspec.yaml client/app/pubspec.lock ./
+RUN flutter pub get
+COPY client/app/ ./
+RUN flutter build web --release
+
+# --- 2. Backend build --------------------------------------------------------
+FROM node:20-bookworm-slim AS api-build
+WORKDIR /src
+COPY backend/package.json backend/package-lock.json ./
+RUN npm ci
+COPY backend/ ./
+RUN npx prisma generate && npm run build
+
+# --- 3. Runtime ------------------------------------------------------------
+FROM node:20-bookworm-slim AS runtime
+ENV NODE_ENV=production
+WORKDIR /app
+# Prisma needs OpenSSL at runtime.
+RUN apt-get update && apt-get install -y --no-install-recommends openssl \
+  && rm -rf /var/lib/apt/lists/*
+COPY --from=api-build /src/node_modules ./node_modules
+COPY --from=api-build /src/dist ./dist
+COPY --from=api-build /src/prisma ./prisma
+# The Flutter web build; app.module reads WEB_CLIENT_DIR.
+COPY --from=web /src/build/web ./web
+ENV WEB_CLIENT_DIR=/app/web
+EXPOSE 3000
+# Apply pending migrations, then boot.
+CMD ["sh", "-c", "npx prisma migrate deploy && node dist/main.js"]