Add business dashboard dark mode from Super Admin theme setting.

Login and in-app surfaces follow tenant themeMode, matching customer dark tokens, with themed switches and tighter card/table chrome.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/business/src/pages/ProductDetailsPage.module.css

@@ -23,7 +23,7 @@
   width: 100%;
   max-width: 320px;
   aspect-ratio: 1 / 1;
-  background: #ffffff;
+  background: var(--card-media-bg);
   border-radius: var(--radius-sm);
   border: 1px solid rgba(148, 163, 184, 0.15);
   overflow: hidden;
@@ -70,7 +70,7 @@
 .thumb {
   width: 52px;
   height: 52px;
-  background: #fff;
+  background: var(--card-media-bg);
   border: 2px solid rgba(148, 163, 184, 0.2);
   border-radius: 8px;
   overflow: hidden;