Add all domain tasks, fix graders, update Docker deps

Dockerfile

@@ -5,6 +5,8 @@ WORKDIR /app
 # Install system dependencies
 RUN apt-get update && apt-get install -y \
     gcc \
+    g++ \
+    git \
     && rm -rf /var/lib/apt/lists/*
 
 # Copy requirements first for layer caching
@@ -18,9 +20,13 @@ COPY . .
 RUN touch app/__init__.py tasks/__init__.py graders/__init__.py data/__init__.py
 
 # HuggingFace Spaces runs as non-root user
-RUN useradd -m -u 1000 user
+RUN useradd -m -u 1000 user && chown -R user:user /app
 USER user
 
+# Pre-download the ML model at BUILD time, not runtime
+# This means first request is instant instead of 30-second delay
+RUN python -c "from sentence_transformers import SentenceTransformer; SentenceTransformer('all-MiniLM-L6-v2')" || true
+
 EXPOSE 7860
 
 ENV PYTHONPATH=/app

requirements.txt

@@ -5,3 +5,6 @@ httpx==0.28.1
 openai==1.58.1
 python-multipart==0.0.20
 pyyaml==6.0.2
+datasets==2.21.0
+huggingface-hub==0.24.0
+sentence-transformers==3.1.1