Add Dockerized FastNext stack template with backend and frontend

Implemented a full-stack template combining Next.js (frontend), FastAPI (backend), and PostgreSQL. Included Docker configurations for development and production, environment file templates, Makefile commands, and initial setup for database migrations and builds. The stack is production-ready and supports hot-reloading for local development.

backend/Dockerfile

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+# Development stage
+FROM python:3.12-slim AS development
+WORKDIR /app
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    PYTHONPATH=/app
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends gcc postgresql-client && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+COPY . .
+COPY entrypoint.sh /usr/local/bin/
+RUN chmod +x /usr/local/bin/entrypoint.sh
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
+
+# Production stage
+FROM python:3.12-slim AS production
+WORKDIR /app
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    PYTHONPATH=/app
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends postgresql-client && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+COPY . .
+COPY entrypoint.sh /usr/local/bin/
+RUN chmod +x /usr/local/bin/entrypoint.sh
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]