refactor(ui): strip all dark: Tailwind classes (single-theme product)

Mechanical sweep of 41 files via `perl -i -pe 's{\s+dark:[\w:/\[\]\.\-]+}{}g'`.
All dark: variants were paired with light-mode counterparts already; no
elements relied on a dark:-only style.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/shared/requirement-upload-slot.tsx

@@ -263,9 +263,9 @@ export function RequirementUploadSlot({
 
   const isFulfilled = !!existingFile
   const statusColor = isFulfilled
-    ? 'border-green-200 bg-green-50 dark:border-green-900 dark:bg-green-950'
+    ? 'border-green-200 bg-green-50'
     : requirement.isRequired
-      ? 'border-red-200 bg-red-50 dark:border-red-900 dark:bg-red-950'
+      ? 'border-red-200 bg-red-50'
       : 'border-muted'
 
   // Build accept string for file input