feat(ui): wire SvelteKit into docker-compose with ui service and env vars

ui/Dockerfile

@@ -0,0 +1,23 @@
+FROM node:22-alpine AS builder
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+RUN npm ci
+
+COPY . .
+RUN npm run build
+
+# ── Runtime image ──────────────────────────────────────────────────────────────
+FROM node:22-alpine
+WORKDIR /app
+
+# adapter-node produces a standalone build/
+COPY --from=builder /app/build ./build
+COPY --from=builder /app/package.json ./
+
+ENV NODE_ENV=production
+ENV PORT=3000
+ENV HOST=0.0.0.0
+
+EXPOSE 3000
+CMD ["node", "build"]