fix: optimize Dockerfile with --prefer-binary for faster builds

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via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

Dockerfile

@@ -9,9 +9,12 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     proj-bin \
     && rm -rf /var/lib/apt/lists/*
 
+# Install dependencies first (cached layer)
 COPY pyproject.toml .
-RUN pip install --no-cache-dir .
+COPY app/__init__.py app/__init__.py
+RUN pip install --no-cache-dir --prefer-binary .
 
+# Copy application code
 COPY app/ app/
 COPY frontend/ frontend/