Use local source instead of fetching from GitHub in Docker build

[magnified103]

judge-server/.docker/tier1/Dockerfile

Lines 16 to 18 in c0fce0a

	RUN mkdir /judge /problems && cd /judge && \
	curl -L https://github.com/VNOI-Admin/judge-server/archive/"${TAG}".tar.gz | tar -xz --strip-components=1 && \
	python3 -m venv --prompt=DMOJ /env && \

The Dockerfile currently fetches the source code directly from GitHub during the build stage. This makes local development inconvenient because developers must push changes to a specific branch before they can build the image.