Make the offline RAG chain observable without widening credential access

Expose the verified synthetic retrieval path through a typed React client and a non-root Nginx edge while keeping database credentials and data-network reachability out of the browser tier. A fixed-origin gateway preserves request boundaries and now closes upstream streams even when downstream disconnects before body iteration. The deployment ADR and runbooks record the four-network topology and its accepted Web edge-egress risk.

Constraint: The previously exposed Bailian key must be revoked and no live provider credential may enter Git, images, logs, or the browser.
Rejected: Connect Web directly to the data network | expands lateral reach to PostgreSQL.
Rejected: Publish the database-aware API on the edge network | gives a credential-bearing process a public default route.
Rejected: Buffer streaming responses in either proxy | prevents incremental chat delivery in the future.
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Do not mark Stage 1 or Stage 2 complete until the rotated-key live smoke and remaining stage gates pass.
Tested: make verify; 65 backend tests; 14 frontend tests; Docker image build; container health and isolation probes; real HTTP demo/status/search/docs/OpenAPI checks.
Not-tested: Live Bailian models, real document ingestion, business chat SSE generation, and final browser screenshot automation because the browser skill runtime was unavailable.

frontend/Dockerfile

@@ -0,0 +1,25 @@
+# syntax=docker/dockerfile:1.7@sha256:a57df69d0ea827fb7266491f2813635de6f17269be881f696fbfdf2d83dda33e
+FROM node:22-alpine@sha256:16e22a550f3863206a3f701448c45f7912c6896a62de43add43bb9c86130c3e2 AS build
+
+ENV CI=true
+
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+RUN npm ci
+
+COPY . .
+RUN npm run build
+
+FROM nginxinc/nginx-unprivileged:1.29-alpine@sha256:0c79d56aee561a1d81c63f00eee5fb5fe29279560cdc55e91425133104c7fbe6 AS runtime
+
+COPY nginx.conf /etc/nginx/nginx.conf
+COPY --chown=101:101 --from=build /app/dist /usr/share/nginx/html
+
+USER 101:101
+EXPOSE 8080
+
+# The configuration is immutable and does not use envsubst templates, so skip
+# the base entrypoint's mutation probes against the read-only filesystem.
+ENTRYPOINT ["nginx"]
+CMD ["-g", "daemon off;"]