Fix automatic readable text contrast for public and admin themes.

Derive admin/public text colors from WCAG contrast, unify ThemeVars CSS emission, and keep navbar overrides in sync with readable vars.

Co-authored-by: Cursor <[email protected]>

src/app/admin/layout.tsx

@@ -402,7 +402,7 @@ async function Sidebar({
 		>
 			<div className="flex items-center gap-3 px-4 py-5 border-b border-[var(--admin-border)]">
 				<span
-					className="flex-none w-10 h-10 rounded-xl grid place-items-center font-extrabold text-base text-[var(--color-primary-foreground-readable)] bg-[var(--admin-accent)] shadow-lg shadow-[var(--admin-accent)]/20"
+					className="flex-none w-10 h-10 rounded-xl grid place-items-center font-extrabold text-base text-[var(--admin-accent-foreground)] bg-[var(--admin-accent)] shadow-lg shadow-[var(--admin-accent)]/20"
 					aria-hidden
 				>
 					{initial}
@@ -475,7 +475,7 @@ async function Topbar({
 				<span className="text-xs text-[var(--admin-text-muted)]">
 					<strong className="text-[var(--admin-text)]">{staff.username}</strong>
 				</span>
-				<span className="inline-flex items-center gap-1.5 text-[0.6rem] font-bold uppercase tracking-wider text-[var(--color-primary-foreground-readable)] bg-[var(--admin-accent)] rounded-full px-2.5 py-1">
+				<span className="inline-flex items-center gap-1.5 text-[0.6rem] font-bold uppercase tracking-wider text-[var(--admin-accent-foreground)] bg-[var(--admin-accent)] rounded-full px-2.5 py-1">
 					{t("rankLabel", { rank: staff.rank })}
 				</span>
 			</div>

src/app/admin/theme/color-field.tsx

@@ -73,7 +73,17 @@ export function ColorField({
 				type="color"
 				name={name}
 				value={val}
-				onChange={(e) => setVal(e.target.value)}
+				onChange={(e) => {
+					const next = e.target.value;
+					if (bgValue) {
+						const nextRatio = contrastRatio(next, bgValue);
+						if (nextRatio != null && nextRatio < 4.5) {
+							setVal(readableOn(bgValue));
+							return;
+						}
+					}
+					setVal(next);
+				}}
 				style={{
 					width: 42,
 					height: 36,