fix(api): install gcc before user switch to enable hdbscan compilation

Dockerfile

@@ -1,11 +1,13 @@
 FROM python:3.12-slim
 
-# HF Spaces runs as non-root user
+# Install build tools as root BEFORE switching user
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    gcc g++ make \
+    && rm -rf /var/lib/apt/lists/*
+
 RUN useradd -m -u 1000 user
 USER user
 ENV PATH="/home/user/.local/bin:$PATH"
-
-# Redirect ALL model/cache writes to /tmp (only writable dir on HF Spaces)
 ENV HF_HOME=/tmp/hf-cache
 ENV TRANSFORMERS_CACHE=/tmp/hf-cache
 ENV TORCH_HOME=/tmp/torch-cache
@@ -13,14 +15,9 @@ ENV XDG_CACHE_HOME=/tmp/cache
 ENV TOKENIZERS_PARALLELISM=false
 
 WORKDIR /app
-
-# Install dependencies first (layer caching)
 COPY --chown=user requirements.txt .
 RUN pip install --no-cache-dir --upgrade -r requirements.txt
-
-# Copy app code
 COPY --chown=user . /app
 
-# HF Spaces requires port 7860
 EXPOSE 7860
 CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "7860"]