feat: 특이사항(CUSETC) 영수증 인쇄 기능 추가

- pos_printer.py: print_cusetc() 함수 추가 (ESC/POS 영수증 출력)
- admin.html: 회원 상세 모달에 🖨️ 인쇄 버튼 추가
- 즉시 피드백 토스트 + API 응답 후 결과 표시

backend/templates/admin.html

@@ -20,6 +20,41 @@
             -webkit-font-smoothing: antialiased;
         }
 
+        /* 토스트 알림 */
+        .toast-container {
+            position: fixed;
+            top: 20px;
+            right: 20px;
+            z-index: 10000;
+            display: flex;
+            flex-direction: column;
+            gap: 10px;
+        }
+        .toast {
+            padding: 14px 20px;
+            border-radius: 10px;
+            color: white;
+            font-weight: 500;
+            font-size: 14px;
+            box-shadow: 0 4px 12px rgba(0,0,0,0.15);
+            animation: toastIn 0.3s ease, toastOut 0.3s ease 2.7s forwards;
+            display: flex;
+            align-items: center;
+            gap: 10px;
+        }
+        .toast.success { background: linear-gradient(135deg, #10b981 0%, #059669 100%); }
+        .toast.error { background: linear-gradient(135deg, #ef4444 0%, #dc2626 100%); }
+        .toast.info { background: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%); }
+        .toast.printing { background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%); }
+        @keyframes toastIn {
+            from { opacity: 0; transform: translateX(100px); }
+            to { opacity: 1; transform: translateX(0); }
+        }
+        @keyframes toastOut {
+            from { opacity: 1; transform: translateX(0); }
+            to { opacity: 0; transform: translateX(100px); }
+        }
+
         .header {
             background: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
             padding: 32px 24px;
@@ -944,31 +979,53 @@
             if (editBtn) editBtn.style.display = 'inline-block';
         }
         
-        // 특이사항 인쇄
-        async function printCusetc(customerName, cusetc, phone) {
-            if (!confirm(`${customerName}님의 특이사항을 인쇄하시겠습니까?`)) {
-                return;
+        // 토스트 알림 함수
+        function showToast(message, type = 'info') {
+            let container = document.querySelector('.toast-container');
+            if (!container) {
+                container = document.createElement('div');
+                container.className = 'toast-container';
+                document.body.appendChild(container);
             }
             
+            const toast = document.createElement('div');
+            toast.className = `toast ${type}`;
+            
+            const icons = { success: '✅', error: '❌', info: 'ℹ️', printing: '🖨️' };
+            toast.innerHTML = `<span>${icons[type] || ''}</span><span>${message}</span>`;
+            
+            container.appendChild(toast);
+            
+            setTimeout(() => toast.remove(), 3000);
+        }
+        
+        // 인쇄용 전역 변수
+        let printData = { name: '', cusetc: '', phone: '' };
+        
+        // 특이사항 인쇄 실행
+        async function doPrintCusetc() {
+            // 즉시 피드백
+            showToast(`${printData.name}님 특이사항 인쇄 중...`, 'printing');
+            
             try {
                 const res = await fetch('/api/print/cusetc', {
                     method: 'POST',
                     headers: { 'Content-Type': 'application/json' },
                     body: JSON.stringify({
-                        customer_name: customerName,
-                        cusetc: cusetc,
-                        phone: phone
+                        customer_name: printData.name,
+                        cusetc: printData.cusetc,
+                        phone: printData.phone
                     })
                 });
                 const data = await res.json();
                 
                 if (data.success) {
-                    alert('🖨️ ' + data.message);
+                    showToast(data.message, 'success');
                 } else {
-                    alert('❌ 인쇄 실패: ' + (data.error || '알 수 없는 오류'));
+                    showToast('인쇄 실패: ' + (data.error || '알 수 없는 오류'), 'error');
                 }
             } catch (err) {
-                alert('❌ 오류: ' + err.message);
+                showToast('오류: ' + err.message, 'error');
             }
         }
 
@@ -1015,7 +1072,7 @@
                             <div style="display: flex; align-items: center; gap: 8px; margin-bottom: 6px;">
                                 <span style="color: #d97706; font-size: 13px;">⚠️ 특이사항</span>
                                 <button onclick="editCusetc('${data.pos_customer.cuscode}', this)" style="background: none; border: 1px solid #d97706; color: #d97706; font-size: 11px; padding: 2px 8px; border-radius: 4px; cursor: pointer;">✏️ 수정</button>
-                                ${data.pos_customer.cusetc ? `<button onclick="printCusetc('${data.pos_customer.name}', '${(data.pos_customer.cusetc || '').replace(/'/g, "\\'")}', '${user.phone || ''}')" style="background: none; border: 1px solid #6b7280; color: #6b7280; font-size: 11px; padding: 2px 8px; border-radius: 4px; cursor: pointer;">🖨️ 인쇄</button>` : ''}
+                                ${data.pos_customer.cusetc ? `<button onclick="printData={name:'${data.pos_customer.name}',cusetc:decodeURIComponent('${encodeURIComponent(data.pos_customer.cusetc)}'),phone:'${user.phone||''}'};doPrintCusetc()" style="background: none; border: 1px solid #6b7280; color: #6b7280; font-size: 11px; padding: 2px 8px; border-radius: 4px; cursor: pointer;">🖨️ 인쇄</button>` : ''}
                             </div>
                             <div id="cusetc-view" onclick="toggleCusetc(this)" style="color: #92400e; font-size: 14px; font-weight: 500; cursor: ${(data.pos_customer.cusetc || '').length > 30 ? 'pointer' : 'default'}; ${(data.pos_customer.cusetc || '').length > 30 ? 'max-height: 40px; overflow: hidden;' : ''}" title="${(data.pos_customer.cusetc || '').length > 30 ? '클릭하여 펼치기' : ''}">
                                 ${data.pos_customer.cusetc || '<span style="color: #9ca3af; font-weight: normal;">없음</span>'}