latexgrambot: inline LaTeX bot for Telegram in Go

Renders LaTeX expressions into PNG pictures, PDF documents and native
Telegram rich text messages, entirely locally with TeX Live and poppler.

- Chat mode with /image, /pdf, /rich plus per-user preamble and DPI
- Inline mode delivering picture, PDF and rich text results
- Broad default package set preloaded into a TeX format at image build
- MongoDB persistence: settings, users, groups, render statistics
- Private S3-compatible bucket with short-lived presigned URLs
- OpenTelemetry traces over OTLP
- Kubernetes manifests and Argo CD application, Docker Compose, GitHub
  Actions CI, BSD 3-Clause license

Dockerfile

@@ -0,0 +1,39 @@
+FROM golang:1.23-alpine AS build
+
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+ARG TARGETOS
+ARG TARGETARCH
+RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} \
+    go build -trimpath -ldflags="-s -w" -o /latexgrambot ./cmd/latexgrambot
+
+# Runtime: TeX Live (pdflatex) and poppler (pdftoppm). The latex-extra,
+# pictures, science and plain-generic collections cover the broad default
+# preamble (tikz, pgfplots, siunitx, mhchem, chemfig, ...).
+FROM debian:bookworm-slim
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        ca-certificates tzdata \
+        texlive-latex-base texlive-latex-recommended texlive-fonts-recommended \
+        texlive-latex-extra texlive-pictures texlive-science texlive-plain-generic \
+        lmodern poppler-utils \
+    && rm -rf /var/lib/apt/lists/* \
+    && adduser --disabled-password --gecos "" --uid 1000 appuser
+COPY --from=build /latexgrambot /usr/local/bin/latexgrambot
+
+# Preload the default document class and package set into a TeX format, so
+# every render skips loading ~50 packages (about a second per compile).
+RUN mkdir -p /tmp/format \
+    && /usr/local/bin/latexgrambot -print-preamble > /tmp/format/preamble.tex \
+    && cd /tmp/format \
+    && pdflatex -ini -jobname=latexgrambot "&pdflatex" mylatexformat.ltx preamble.tex >/dev/null \
+    && install -d /usr/local/share/texmf/web2c \
+    && install -m 0644 /tmp/format/latexgrambot.fmt /usr/local/share/texmf/web2c/latexgrambot.fmt \
+    && mktexlsr \
+    && rm -rf /tmp/format
+
+USER appuser
+EXPOSE 8080
+ENTRYPOINT ["/usr/local/bin/latexgrambot"]