Cream page background end-to-end: Dockerfile PWA colors, README, verify block

Follow-up to the custom.css/custom2.js change: the Dockerfile seds the web
manifest theme_color/background_color and the index.html light meta to
#eaf3ea, and the README's verify block asserted the green wash as correct
("an earlier version of this block asserted cream ... would have led you to
fix a correct deploy"). Both are the same regression: the wash was rejected
earlier, restored by accident, and then documented as intended.

- Dockerfile: manifest + index meta -> #faf8f5 (cream), with an explicit
  "keep these three in sync" note (this sed, custom.css html:not(.dark),
  custom2.js COOP_BG.light).
- README verify block: asserts cream again, plus a new step for the
  install-time colors no DOM check covers (manifest + light meta).
- README palette section: hover is #f0ede6 not the wash; --presentation is
  cream; source of truth is the DEPLOYED CSS of dashboard/portal/panel, with
  the read command; records the shared 4.32:1 / 3.93:1 accessibility caveat;
  notes that cloudron exec silently swallows multi-line sh -c.

Dockerfile

@@ -67,12 +67,15 @@ RUN python3 /app/code/patch_index.py && \
 
 # PWA chrome colors: LibreChat ships a teal theme_color (#009688) in the web
 # manifest (the bright green bar Firefox PWAs draw across the top) and black
-# background_color. Point both at the light page color (#eaf3ea dashboard green
-# wash — the manifest can only hold one value; custom2.js re-syncs the meta
-# tags to the app's actual theme at runtime). The index.html meta gets a
-# light + dark pair so browser/PWA chrome matches the phone theme natively.
-RUN sed -i 's|"theme_color": *"#009688"|"theme_color":"#eaf3ea"|; s|"background_color": *"#000000"|"background_color":"#eaf3ea"|' /app/code/librechat/client/dist/manifest.webmanifest && \
-    sed -i 's|<meta name="theme-color" content="#171717" />|<meta name="theme-color" media="(prefers-color-scheme: light)" content="#eaf3ea" />\n    <meta name="theme-color" media="(prefers-color-scheme: dark)" content="#22271f" />|' /app/code/librechat/client/dist/index.html
+# background_color. Point both at the light page color — CREAM #faf8f5, the
+# dashboard's page background (the manifest can only hold one value; custom2.js
+# re-syncs the meta tags to the app's actual theme at runtime). The index.html
+# meta gets a light + dark pair so browser/PWA chrome matches the phone theme
+# natively. KEEP THESE THREE IN SYNC: this sed, custom.css's html:not(.dark)
+# background, and custom2.js COOP_BG.light — the green wash #eaf3ea used to sit
+# in all three and made the installed app read as green.
+RUN sed -i 's|"theme_color": *"#009688"|"theme_color":"#faf8f5"|; s|"background_color": *"#000000"|"background_color":"#faf8f5"|' /app/code/librechat/client/dist/manifest.webmanifest && \
+    sed -i 's|<meta name="theme-color" content="#171717" />|<meta name="theme-color" media="(prefers-color-scheme: light)" content="#faf8f5" />\n    <meta name="theme-color" media="(prefers-color-scheme: dark)" content="#22271f" />|' /app/code/librechat/client/dist/index.html
 
 # Log ownership guard: a host-side daily job creates the next day's dated log
 # files in /app/data/logs as root:root at 00:00 UTC; LibreChat (cloudron user)