Switch from ADD to COPY in Dockerfile

This change updates the Dockerfile to use the COPY instruction instead of ADD. COPY is preferred when only copying files because it is more explicit and simpler.

Author: coordt

Dockerfile

@@ -11,7 +11,7 @@ RUN --mount=type=cache,target=/root/.cache/uv \
 #    --mount=type=bind,source=uv.lock,target=uv.lock \
 #    --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
     uv sync --frozen --no-install-project --no-dev
-ADD . /app
+COPY . /app
 RUN --mount=type=cache,target=/root/.cache/uv \
     uv sync --frozen --no-dev