refactor: 전체 프론트엔드 하드코딩 색상 → CSS 변수 일괄 치환

447+ 파일, 4500+ 줄 변경:
- gray-* → border/bg-muted/text-foreground/text-muted-foreground
- blue-* → primary/ring
- red-* → destructive
- green-* → emerald (일관성)
- indigo-* → primary
- yellow/orange → amber (통일)
- dark mode 변형도 시맨틱 토큰으로 변환

Made-with: Cursor

frontend/app/(main)/admin/automaticMng/mail/sent/page.tsx

@@ -371,8 +371,8 @@ export default function SentMailPage() {
                   {stats.successCount}
                 </p>
               </div>
-              <div className="p-3 bg-green-500/10 rounded-lg">
-                <CheckCircle2 className="w-6 h-6 text-green-600" />
+              <div className="p-3 bg-emerald-500/10 rounded-lg">
+                <CheckCircle2 className="w-6 h-6 text-emerald-600" />
               </div>
             </div>
           </CardContent>
@@ -387,8 +387,8 @@ export default function SentMailPage() {
                   {stats.failedCount}
                 </p>
               </div>
-              <div className="p-3 bg-red-500/10 rounded-lg">
-                <XCircle className="w-6 h-6 text-red-600" />
+              <div className="p-3 bg-destructive/10 rounded-lg">
+                <XCircle className="w-6 h-6 text-destructive" />
               </div>
             </div>
           </CardContent>
@@ -403,8 +403,8 @@ export default function SentMailPage() {
                   {stats.todayCount}
                 </p>
               </div>
-              <div className="p-3 bg-blue-500/10 rounded-lg">
-                <Calendar className="w-6 h-6 text-blue-600" />
+              <div className="p-3 bg-primary/10 rounded-lg">
+                <Calendar className="w-6 h-6 text-primary" />
               </div>
             </div>
           </CardContent>