Add production Dockerfile for backend deployment

backend/Dockerfile

@@ -0,0 +1,19 @@
+FROM python:3.12-slim
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1
+
+WORKDIR /app
+
+# Install runtime dependencies from local package metadata.
+COPY pyproject.toml /app/pyproject.toml
+COPY app /app/app
+COPY scripts /app/scripts
+COPY README.md /app/README.md
+
+RUN pip install --no-cache-dir --upgrade pip && \
+    pip install --no-cache-dir .
+
+EXPOSE 8000
+
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]