fix: include MANIFEST.in in Docker build for template files

The MANIFEST.in file tells setuptools to include Jinja2 templates
in the package. Without it, the templates directory is not installed.

Author: dvershinin

Dockerfile

@@ -3,7 +3,7 @@ FROM python:alpine
 WORKDIR /src
 
 # Copy only the files needed for pip install
-COPY setup.py pyproject.toml ./
+COPY setup.py pyproject.toml MANIFEST.in ./
 COPY gixy/ ./gixy/
 
 RUN pip install --upgrade pip setuptools wheel && pip install .