fix: Dockerfile README.md in deps layer for hatchling build

Dockerfile

@@ -8,7 +8,7 @@ COPY --from=ghcr.io/astral-sh/uv:latest /uv /uvx /usr/local/bin/
 WORKDIR /app
 
 # Install dependencies first for layer caching (source changes don't invalidate)
-COPY pyproject.toml ./
+COPY pyproject.toml README.md ./
 RUN mkdir -p guarddog_nexus && echo '__version__ = "0.1.0"' > guarddog_nexus/__init__.py
 RUN uv pip install . --system
 RUN uv pip install --system "guarddog>=2.10.0"
@@ -16,7 +16,6 @@ RUN rm -rf guarddog_nexus
 
 # Application source (frequently changes — cached dependency layers preserved)
 COPY guarddog_nexus/ guarddog_nexus/
-COPY README.md ./
 
 RUN mkdir -p /data /tmp/guarddog-nexus