feat: enforce no hardcoded colors across entire CMS

Added scripts/check-admin-colors.mjs — scans all src/ files for:
- text-white, text-black (use theme text vars)
- bg-white, bg-black (use theme background/overlay vars)
- bg/text/border/ring with gray/slate/zinc/stone palette
- bg/text/border/ring with red/green/blue/etc palette

Fixed 21 violations across 11 files:
- Overlays: bg-black/* → bg-foreground/*
- Text: text-white → text-primary-foreground
- Backgrounds: bg-white/10 → bg-background/10
- Green accents: bg-green-* → bg-primary
- Red accents: bg-red-* → bg-destructive

Integrated into:
- lint-staged: runs on every *.ts/*.tsx commit
- vitest: src/lib/no-hardcoded-colors.test.ts replaces old audit test
- Allowlist: shadcn/ui primitives (button, badge, dialog) + 4 graphical files

src/app/admin/prefixes/prefixes-client.tsx

@@ -164,7 +164,7 @@ function PrefixDialog({
 	const hasMultiColor = colors.length > 1 && new Set(colors).size > 1;
 
 	return (
-		<div className="fixed inset-0 z-50 flex items-center justify-center bg-black/50">
+		<div className="fixed inset-0 z-50 flex items-center justify-center bg-foreground/50">
 			<div className="bg-background rounded-lg shadow-lg w-full max-w-md p-6 space-y-4">
 				<div className="flex items-center justify-between">
 					<h3 className="text-lg font-semibold">