Add Docker setup: one script to set up/start/stop the full stack

A new developer needs only Docker Desktop — no local Go, Node, or PostgreSQL.

- docker-compose.yml: PostgreSQL + Go API + Angular (nginx) with healthcheck,
  migrations auto-applied via docker-entrypoint-initdb.d, data in a volume
- backend/Dockerfile: static Go binary on distroless (nonroot)
- frontend/Dockerfile: Angular prod build served by nginx, which proxies /api
  to the api service (same origin, no CORS)
- docker.ps1: setup / start / stop / restart / reset / rebuild / status / logs;
  reads DB creds from backend/.env (single source, nothing duplicated)
- .dockerignore keeps .env and local artifacts out of image build contexts
- README: "Run with Docker" quick start

Not yet run end to end here (Docker is not installed on this machine); the
compose and script are validated for syntax and structure.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/Dockerfile

@@ -0,0 +1,17 @@
+# --- build -----------------------------------------------------------------
+FROM node:24-alpine AS build
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+RUN npm ci
+
+COPY . .
+RUN npm run build
+# Angular's application builder emits the browser bundle to dist/frontend/browser.
+
+# --- runtime ---------------------------------------------------------------
+FROM nginx:1.27-alpine
+# Serve the SPA and proxy /api to the api service (same origin, so no CORS).
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY --from=build /app/dist/frontend/browser /usr/share/nginx/html
+EXPOSE 80