fix: BigInt JSON serialization, pricing table dark mode

- Add BigInt.prototype.toJSON polyfill in main.ts so Express can
  serialize Prisma BigInt fields (priceVND, revenue amounts)
- Fix: admin/moderation and admin/revenue returning 500 Internal Error
- Fix pricing compare table: Enterprise column text invisible in dark
  mode (bg-green-50 without dark variant → add dark:bg-green-950/40)

Co-Authored-By: Claude Opus 4 (1M context) <noreply@anthropic.com>

apps/api/src/main.ts

@@ -1,5 +1,11 @@
 import './instrument';
 
+// BigInt cannot be serialized by JSON.stringify by default.
+// Polyfill toJSON so Express/NestJS can serialize Prisma BigInt fields.
+(BigInt.prototype as any).toJSON = function () {
+  return this.toString();
+};
+
 import { RequestMethod, ValidationPipe } from '@nestjs/common';
 import { NestFactory } from '@nestjs/core';
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';

apps/web/app/[locale]/(public)/pricing/page.tsx

@@ -525,7 +525,7 @@ export default function PricingPage() {
                       className={cn(
                         'px-4 py-3 text-center text-sm font-semibold',
                         plan.tier === 'AGENT_PRO' && 'bg-primary/5',
-                        isAuthenticated && plan.tier === currentTier && 'bg-green-50',
+                        isAuthenticated && plan.tier === currentTier && 'bg-green-50 dark:bg-green-950/40',
                       )}
                     >
                       <span>{t(`tiers.${plan.tier}`)}</span>
@@ -552,7 +552,7 @@ export default function PricingPage() {
                           className={cn(
                             'px-4 py-3 text-center text-sm',
                             plan.tier === 'AGENT_PRO' && 'bg-primary/5',
-                            isAuthenticated && plan.tier === currentTier && 'bg-green-50',
+                            isAuthenticated && plan.tier === currentTier && 'bg-green-50 dark:bg-green-950/40',
                           )}
                         >
                           {typeof val === 'boolean' ? (