Split server Dockerfile into smaller layers

The 413 from git.thumeit.com was on a single blob PUT, not the whole
image -- split the Node.js apt install and the render-service npm
install into several smaller RUN layers (purging curl/gnupg in the
same layer they're installed in, cleaning npm's cache after each
package) so no single pushed blob is as large as before.

server/Dockerfile

@@ -2,31 +2,58 @@ FROM python:3.12-slim
 
 WORKDIR /app
 
-# tzdata: python:3.12-slim doesn't include it by default, so the zoneinfo
-# database backing the web UI's "Timezone" setting (used by "Quiet hours")
-# would have no named zones to resolve without this -- ZoneInfo() would
-# raise for anything other than "UTC".
-#
-# Node.js + fonts: whiteboard frame mode's render-service/ (own README
-# there) runs as a second process in this same container rather than a
-# separate compose service -- it's a lightweight, stateless, localhost-
-# only sidecar with nothing worth independently scaling or restarting.
-# NodeSource's setup script is used instead of Debian bookworm's own
-# apt Node package, which is both older than jsdom's minimum (20.19+)
-# and inconsistently available. fonts-dejavu-core gives the sidecar's
-# SVG rasterizer something to render whiteboard text with.
+# tzdata/fonts in their own layer, kept separate from the much larger
+# Node.js/npm layers below -- see those layers' own comments for why
+# they're split up the way they are. tzdata: python:3.12-slim doesn't
+# include it by default, so the zoneinfo database backing the web UI's
+# "Timezone" setting (used by "Quiet hours") would have no named zones
+# to resolve without this -- ZoneInfo() would raise for anything other
+# than "UTC". fontconfig/fonts-dejavu-core: whiteboard mode's
+# render-service/ (own README there) needs something to render
+# whiteboard text with.
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    tzdata curl ca-certificates gnupg fontconfig fonts-dejavu-core \
+    tzdata fontconfig fonts-dejavu-core \
+    && rm -rf /var/lib/apt/lists/*
+
+# Node.js: whiteboard frame mode's render-service/ runs as a second
+# process in this same container rather than a separate compose service
+# -- it's a lightweight, stateless, localhost-only sidecar with nothing
+# worth independently scaling or restarting. NodeSource's setup script is
+# used instead of Debian bookworm's own apt Node package, which is both
+# older than jsdom's minimum (20.19+) and inconsistently available.
+# curl/gnupg are only needed to add and fetch NodeSource's repo -- purged
+# again in this same RUN (not a later one; Docker layers are immutable,
+# so removing them in a *different* instruction wouldn't shrink this
+# one's actual pushed size) so their bytes don't end up in the image at
+# all, only nodejs's.
+RUN apt-get update && apt-get install -y --no-install-recommends curl ca-certificates gnupg \
     && curl -fsSL https://deb.nodesource.com/setup_22.x | bash - \
     && apt-get install -y --no-install-recommends nodejs \
+    && apt-get purge -y --auto-remove curl gnupg \
     && rm -rf /var/lib/apt/lists/*
 
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
-COPY render-service ./render-service
-RUN cd render-service && npm install --omit=dev
+# render-service/'s dependencies installed as several separate layers
+# rather than one `npm install` covering all of them -- a from-scratch
+# push of this image once hit Cloudflare's payload-size limit on a
+# single blob/layer upload (the registry sits behind it), and splitting
+# a big layer into several smaller ones is the direct fix for exactly
+# that failure mode, independent of anything about the registry itself.
+# --no-save: package.json already fully declares these (with the exact
+# same version pins used here) as the single source of truth for what
+# this service depends on -- these calls are just about *when* each one
+# gets installed for layer-size reasons, not re-deciding what's needed.
+COPY render-service/package.json ./render-service/package.json
+WORKDIR /app/render-service
+RUN npm install --omit=dev --no-save express@^5.2.1 && npm cache clean --force
+RUN npm install --omit=dev --no-save jsdom@^29.1.1 && npm cache clean --force
+RUN npm install --omit=dev --no-save @excalidraw/[email protected] && npm cache clean --force
+RUN npm install --omit=dev --no-save @resvg/[email protected] && npm cache clean --force
+WORKDIR /app
 
+COPY render-service/server.js ./render-service/server.js
 COPY app ./app
 COPY start.sh .
 RUN chmod +x start.sh