perf: PyTorch CPU-only + pip cache cleanup to reduce Docker image size (~3GB savings)

Dockerfile

@@ -8,21 +8,34 @@ ENV PYTHONDONTWRITEBYTECODE=1 \
 
 WORKDIR /app
 
+# System deps: ffmpeg for video processing
 RUN apt-get update \
     && apt-get install -y --no-install-recommends \
         ffmpeg \
         curl \
     && rm -rf /var/lib/apt/lists/*
 
+# Install PyTorch CPU-only first (saves ~1.5GB vs GPU version)
+RUN pip install --no-cache-dir torch==2.11.0 --index-url https://download.pytorch.org/whl/cpu
+
+# Install remaining Python deps
 COPY requirements.txt ./
-RUN pip install --upgrade pip \
-    && pip install -r requirements.txt \
-    && pip install pytest
+RUN pip install --no-cache-dir --upgrade pip \
+    && pip install --no-cache-dir -r requirements.txt
 
+# Install Chromium for Playwright (already cached at /ms-playwright)
 RUN python -m playwright install --with-deps chromium
 
+# Clean up pip cache and temp files
+RUN pip cache purge 2>/dev/null || true \
+    && find /usr/local/lib/python3.14 -name '__pycache__' -exec rm -rf {} + 2>/dev/null || true \
+    && find /usr/local/lib/python3.14 -name '*.pyc' -delete 2>/dev/null || true \
+    && rm -rf /root/.cache
+
+# Copy app code
 COPY . .
 
+# Create non-root user
 RUN groupadd -r appuser && useradd -r -g appuser -d /app appuser \
     && chown -R appuser:appuser /app /ms-playwright