fix: Blueprint catalog dark theme — use solid backgrounds, stronger contrast

- Field cards inactive: dark:bg-gray-800 (solid, no opacity)
- Field cards active: dark:bg-brand-950/60 with dark:border-brand-600/50
- Sidebar: dark:bg-slate-800/80 (darker than modal background)
- Sidebar active item: dark:bg-brand-900/60 (visible brand tint)
- Sidebar hover: dark:hover:bg-gray-700/60
- Custom field form: dark:bg-gray-800 (solid)
- Dispo import subtitle text update

Co-Authored-By: claude-flow <ruv@ruv.net>

apps/web/src/components/blueprints/FieldCard.tsx

@@ -83,8 +83,8 @@ export function FieldCard({ field, overrides, onChange }: FieldCardProps) {
     <div
       className={`border rounded-lg transition-all ${
         isActive
-          ? "border-brand-300 bg-brand-50/40 shadow-sm dark:border-brand-700 dark:bg-brand-950/30"
-          : "border-gray-200 bg-white dark:border-gray-700 dark:bg-gray-800/50"
+          ? "border-brand-400/60 bg-brand-50/40 shadow-sm dark:border-brand-600/50 dark:bg-brand-950/60"
+          : "border-gray-200 bg-white dark:border-gray-700/50 dark:bg-gray-800"
       }`}
     >
       {/* Header row */}