Light theme: cream page background and warm neutrals, matching the dashboard

v3 used the green wash #eaf3ea for --surface-primary, the page background,
which read as too green. Replaced with the palette read from the DEPLOYED
CSS of the dashboard, portal and panel (identical across all three):

  --surface-primary  #eaf3ea -> #faf8f5 (cream, page background)
  --surface-tertiary green   -> #f4f2ec (warm chip)
  --surface-hover    green   -> #f0ede6 (warm hover)
  --surface-composer-hover   -> #f0ede6
  --border-light     #cde0cb -> #e4e0d8 (warm neutral border)
  --presentation     #eaf3ea -> #faf8f5 (composer band)
  --link             #4a7a4a -> #4e7a4d (deeper green, 4.70:1 on cream)

Accents are unchanged (green-deep #5b8c5a, green-mid #6ba86b) — they are
the earthy greens the co-op design system already uses. Dark mode is
untouched. Also fixed the two hard-coded washes: the #loading-container
flash and the bare html/body background, plus custom2.js COOP_BG.light,
which was still painting the browser/PWA chrome #eaf3ea while the
manifest said cream.

assets/custom2.js

@@ -45,7 +45,7 @@
   // RESOLVED theme (html.dark class — LibreChat applies it from the user's
   // theme setting, which defaults to system = the phone's theme). Falls back
   // to the light/dark media-query pair in index.html when this script is off.
-  var COOP_BG = { light: '#eaf3ea', dark: '#22271f' };
+  var COOP_BG = { light: '#faf8f5', dark: '#22271f' };
   function syncThemeColor() {
     var dark = document.documentElement.classList.contains('dark');
     var metas = document.querySelectorAll('meta[name="theme-color"]');