build: add dockerfile for constructing backend

Dockerfile

@@ -0,0 +1,19 @@
+# Use slim to reduce size
+FROM python:3.13-slim
+
+# Prevent Python from buffering stdout
+ENV PYTHONUNBUFFERED=1
+
+# System deps required for psycopg2 + torch
+RUN apt-get update && apt-get install -y \
+    build-essential \
+    libpq-dev \
+    gcc \
+    curl \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+COPY . .
+CMD ["python", "main.py"]