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>

backend/Dockerfile

@@ -1,13 +1,19 @@
-FROM python:3.12-slim AS base
+# ── Stage 1: build ──────────────────────────────────────────────────────────
+FROM python:3.12-slim AS build
 
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1
 
 WORKDIR /app
 
-# System deps for WeasyPrint
+# Create virtual environment
+RUN python -m venv /opt/venv
+ENV PATH="/opt/venv/bin:$PATH"
+
+# System deps required by WeasyPrint (build time)
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
+        gcc \
         libpango-1.0-0 \
         libpangocairo-1.0-0 \
         libgdk-pixbuf2.0-0 \
@@ -19,8 +25,31 @@ RUN apt-get update && \
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
+# ── Stage 2: runtime ─────────────────────────────────────────────────────────
+FROM python:3.12-slim
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    PATH="/opt/venv/bin:$PATH"
+
+# System deps required by WeasyPrint (runtime)
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+        libpango-1.0-0 \
+        libpangocairo-1.0-0 \
+        libgdk-pixbuf2.0-0 \
+        libcairo2 \
+        libglib2.0-0 && \
+    rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY --from=build /opt/venv /opt/venv
 COPY . .
 
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+
 EXPOSE 8000
 
-CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]
+ENTRYPOINT ["/entrypoint.sh"]