feat: production docker + documentation

- Backend Dockerfile: multi-stage build with venv, gunicorn+uvicorn workers, entrypoint runs alembic then gunicorn
- Frontend Dockerfile: multi-stage with npm ci, nginx:1.27-alpine runtime
- nginx.conf: gzip compression, security headers (X-Frame-Options, X-Content-Type-Options, etc.), static asset caching, correct API proxy preserving /api/ prefix
- docker-compose.yml: production config — db healthcheck, backend healthcheck, frontend depends_on backend healthy, no exposed backend port
- docker-compose.override.yml: dev hot-reload — uvicorn --reload with source mount, npm run dev on port 5173
- Rate limiting: slowapi middleware on /auth/login (10/min) and /auth/register (5/min)
- README.md: full documentation with architecture, quick start, API table, dev/prod instructions, tests
- .env.example: all variables documented with comments
- .gitignore: extended with *.pyc, *.cover, .ruff_cache, frontend/.vite, etc.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/Dockerfile

@@ -1,15 +1,20 @@
+# ── Stage 1: build ──────────────────────────────────────────────────────────
 FROM node:20-alpine AS build
 
 WORKDIR /app
 
 COPY package.json package-lock.json* ./
-RUN npm install
+RUN npm ci
 
 COPY . .
 RUN npm run build
 
-FROM nginx:alpine
+# ── Stage 2: runtime ─────────────────────────────────────────────────────────
+FROM nginx:1.27-alpine
+
 COPY --from=build /app/dist /usr/share/nginx/html
 COPY nginx.conf /etc/nginx/conf.d/default.conf
+
 EXPOSE 80
+
 CMD ["nginx", "-g", "daemon off;"]