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/super-admin/src/utils/lockBodyScroll.ts

@@ -0,0 +1,19 @@
+/** Nested-modal-safe body scroll lock. Restoring a captured overflow value
+ *  leaves `overflow: hidden` on body after overlapping dialogs close. */
+let lockCount = 0
+
+export function lockBodyScroll() {
+  lockCount += 1
+  if (lockCount === 1) {
+    document.documentElement.style.overflow = 'hidden'
+    document.body.style.overflow = 'hidden'
+  }
+}
+
+export function unlockBodyScroll() {
+  lockCount = Math.max(0, lockCount - 1)
+  if (lockCount === 0) {
+    document.documentElement.style.overflow = ''
+    document.body.style.overflow = ''
+  }
+}