fix(ui): use 100dvh body height and coollabs auth glow

Replace min-h-screen with min-height: 100dvh on body for correct
mobile viewport height, and point the auth shell radial glow at
--color-coollabs instead of --color-accent. Add branding CSS tests.

resources/css/app.css

@@ -257,7 +257,8 @@ body {
 body {
     /* overflow-x: clip (not hidden) — hidden creates a scroll containment that
        breaks position:sticky on settings sidebars and other in-page pins. */
-    @apply min-h-screen text-sm font-sans antialiased scrollbar overflow-x-clip;
+    min-height: 100dvh;
+    @apply text-sm font-sans antialiased scrollbar overflow-x-clip;
 }
 
 .coolify-monaco-editor {
@@ -981,7 +982,7 @@ html[data-theme="custom"] textarea:disabled {
     min-height: 100dvh;
     display: flex;
     background:
-        radial-gradient(circle at 50% 0%, color-mix(in oklab, var(--color-accent) 9%, transparent), transparent 34rem),
+        radial-gradient(circle at 50% 0%, color-mix(in oklab, var(--color-coollabs) 9%, transparent), transparent 34rem),
         var(--coollabs-canvas);
     color: #171717;
 }