fix: install git in Dockerfile for pip+git qverify install

Dockerfile

@@ -2,6 +2,13 @@ FROM python:3.11-slim
 
 WORKDIR /app
 
+# git is needed for `pip install` from github URLs (the qverify install
+# below uses pip's git fetcher). python:3.11-slim does not ship git, so
+# install it explicitly and clean up apt lists in the same layer.
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends git \
+    && rm -rf /var/lib/apt/lists/*
+
 # Install verifier-only Python deps. requirements.txt deliberately omits
 # torch / transformers / outlines because the Space does not load Gemma.
 COPY requirements.txt .