Add local Docker deployment and submodules

- docker-compose.yml: builder, nginx web server and a LaTeX container (profile "latex")
  for regenerating the SVG drawings
- Makefile, scripts/fetch.sh, .env.example
- 50ohm, 50ohm-contents-dl and 50ohm-ansible as submodules tracking branch sv

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

docker/latex/Dockerfile

@@ -0,0 +1,34 @@
+# TeX Live (LuaLaTeX + TikZ/CircuiTikZ) + pdftocairo, used to regenerate the SVG drawings
+# from contents/drawings/*.tex in the content repo.
+FROM debian:trixie-slim
+
+ENV DEBIAN_FRONTEND=noninteractive \
+    HOME=/cache \
+    TEXMFVAR=/cache/texmf-var \
+    TEXMFCACHE=/cache/texmf-var \
+    OSFONTDIR=/usr/share/fonts
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        ca-certificates \
+        fontconfig \
+        fonts-linuxlibertine \
+        latexmk \
+        poppler-utils \
+        python3 \
+        texlive-fonts-extra \
+        texlive-fonts-recommended \
+        texlive-lang-european \
+        texlive-lang-german \
+        texlive-latex-base \
+        texlive-latex-extra \
+        texlive-latex-recommended \
+        texlive-luatex \
+        texlive-pictures \
+        texlive-plain-generic \
+        texlive-science \
+    && rm -rf /var/lib/apt/lists/* \
+    && mkdir -p /cache && chmod 777 /cache
+
+COPY build_drawings.py /usr/local/bin/build_drawings.py
+WORKDIR /content
+ENTRYPOINT ["python3", "/usr/local/bin/build_drawings.py"]