refactor(style): update chat layout and scrolling

frontend/styles.css

@@ -1,6 +1,17 @@
 @import "tailwindcss";
 @plugin "@tailwindcss/typography";
 
+:root {
+  /* Top nav clearance - pages use this to pad past the fixed nav. */
+  --nav-h: calc(max(1rem, env(safe-area-inset-top)) + 3rem);
+  background: var(--color-primary-50);
+}
+
+html,
+body {
+  background: var(--color-primary-50);
+}
+
 [x-cloak] {
   display: none !important;
 }