fix: Re-add ultra-minimal Dockerfile to force HF cache refresh v0.3.13

Fresh Dockerfile with only curl installation to avoid apt-get timeout.
HF should now detect the new minimal configuration.

Test: Only curl + gradio + python-dotenv
Goal: Verify Docker infrastructure works on HF Spaces

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,38 @@
+# Ultra-minimal Dockerfile for HF Spaces
+FROM python:3.11-slim
+
+# Set working directory
+WORKDIR /app
+
+# Install only essential system packages (no build tools)
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl \
+    && rm -rf /var/lib/apt/lists/* \
+    && apt-get clean
+
+# Create non-root user
+RUN useradd -m -u 1000 user
+
+# Switch to user
+USER user
+ENV HOME=/home/user \
+    PATH=/home/user/.local/bin:$PATH
+
+WORKDIR $HOME/app
+
+# Copy and install minimal requirements
+COPY --chown=user requirements.txt .
+RUN pip install --user --no-cache-dir -r requirements.txt
+
+# Copy application code
+COPY --chown=user . .
+
+# Expose port
+EXPOSE 7860
+
+# Environment variables
+ENV GRADIO_SERVER_NAME="0.0.0.0" \
+    GRADIO_SERVER_PORT=7860
+
+# Run the test application
+CMD ["python", "simple_test.py"]

version.py

@@ -2,7 +2,7 @@
 Version information for ChatCal Voice-Enabled AI Assistant
 """
 
-__version__ = "0.3.12"
+__version__ = "0.3.13"
 __build_date__ = "2025-08-18"
 __description__ = "Voice-Enabled ChatCal AI Assistant with Hugging Face deployment"