Fetch headless Chromium at container startup instead of build time

build-and-push failed on the last deploy: chromium-headless-shell's
single ~181MB binary can't be split across Docker layers the way this
project's pip/npm installs were (those are many independently-
installable smaller packages; this is one file), and confirmed-failed
to push past the registry's per-layer size limit.

Moves the `playwright install chromium-headless-shell` step from the
Dockerfile to start.sh, caching into PLAYWRIGHT_BROWSERS_PATH on the
/data volume -- only the very first boot on a fresh volume downloads
it, every boot after that is a no-op check. The image itself no longer
grows by ~262MB, so nothing new gets pushed to the registry at all.

server/Dockerfile

@@ -36,8 +36,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     tzdata fontconfig fonts-dejavu-core nodejs npm \
     && rm -rf /var/lib/apt/lists/*
 
-# EXPERIMENTAL, likely unmergeable as-is -- see below. System libs a
-# headless Chromium needs (app/html_render.py, the weather widget's
+# EXPERIMENTAL. System libs a headless Chromium needs (app/html_render.py, the weather widget's
 # opt-in "modern" render style), trimmed from Playwright's own full
 # `install-deps chromium` list to just what a headless (no Xvfb),
 # Latin-text-plus-emoji use case needs: dropped xvfb (only needed for a
@@ -74,23 +73,23 @@ RUN pip install --no-cache-dir pypdfium2==5.12.1
 RUN pip install --no-cache-dir playwright==1.61.0
 RUN pip install --no-cache-dir -r requirements.txt
 
-# KNOWN LIKELY BLOCKER, not resolved by pulling this into its own layer:
-# `playwright install chromium-headless-shell` unpacks to ~262MB, and its
-# single `chrome-headless-shell` binary alone (measured: 181MB) is one
-# file -- unlike the pip/npm splits above (independently-installable
-# smaller packages moved into their own layers), a single 181MB file
-# can't be divided across multiple <100MB Docker layers by any ordinary
-# COPY/RUN restructuring; the whole file lands in whichever layer's diff
-# contains it. This almost certainly exceeds the same Cloudflare single-
-# blob/layer limit that forced the pip/npm splits elsewhere in this file
-# (see their comments) -- an actual push to this project's registry
-# hasn't been attempted (would require pushing to `main`, which triggers
-# deploy) to confirm, but there is no reason to expect a single 181MB
-# blob to fit where combined ~113MB of many small wheels didn't. Needs a
-# real resolution (a registry without this limit, hosting the browser
-# binary outside the image, etc.) before this branch can actually ship --
-# tracked as open, not silently assumed away.
-RUN playwright install chromium-headless-shell
+# The headless Chromium binary itself is deliberately NOT installed
+# here at build time. `playwright install chromium-headless-shell`
+# unpacks to ~262MB, and its single `chrome-headless-shell` binary alone
+# (measured: 181MB) is one file -- unlike the pip/npm splits above
+# (independently-installable smaller packages moved into their own
+# layers), a single 181MB file can't be divided across multiple <100MB
+# Docker layers by any ordinary COPY/RUN restructuring; the whole file
+# lands in whichever layer's diff contains it, which confirmed-failed
+# to push to this project's registry (the same Cloudflare single-blob/
+# layer limit that forced the pip/npm splits elsewhere in this file --
+# see their comments). Fix: start.sh downloads it at container startup
+# instead, cached on the /data volume (PLAYWRIGHT_BROWSERS_PATH below)
+# so it survives restarts/redeploys and only ever downloads once per
+# volume, not once per image layer. Trade-off: first boot on a fresh
+# volume needs network access to Playwright's CDN -- true of Immich/
+# weather API access too, so not a new requirement for this server.
+ENV PLAYWRIGHT_BROWSERS_PATH=/data/.playwright-browsers
 
 # render-service/'s dependencies installed as several separate layers
 # rather than one `npm install` covering all of them -- a from-scratch