Replace browser confirm dialog with custom modal

Add custom confirmation modal for file deletion with smooth animations and backdrop blur. Improves UI consistency and provides better user experience than default browser dialogs.

src/templates/index.html

@@ -180,6 +180,87 @@
             color: #718096;
             opacity: 0.8;
         }
+
+        .modal-overlay {
+            display: none;
+            position: fixed;
+            top: 0;
+            left: 0;
+            right: 0;
+            bottom: 0;
+            background: rgba(0, 0, 0, 0.5);
+            backdrop-filter: blur(4px);
+            z-index: 1000;
+            align-items: center;
+            justify-content: center;
+        }
+
+        .modal-overlay.active {
+            display: flex;
+        }
+
+        .modal {
+            background: white;
+            border-radius: 1rem;
+            padding: 2rem;
+            max-width: 400px;
+            width: 90%;
+            box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
+            animation: modalSlideIn 0.3s ease-out;
+        }
+
+        @keyframes modalSlideIn {
+            from {
+                opacity: 0;
+                transform: translateY(-20px);
+            }
+            to {
+                opacity: 1;
+                transform: translateY(0);
+            }
+        }
+
+        .modal h2 {
+            color: #2d3748;
+            font-size: 1.5rem;
+            margin-bottom: 1rem;
+            font-weight: 600;
+        }
+
+        .modal p {
+            color: #4a5568;
+            font-size: 1rem;
+            margin-bottom: 1.5rem;
+            line-height: 1.5;
+        }
+
+        .modal-buttons {
+            display: flex;
+            gap: 0.75rem;
+            justify-content: flex-end;
+        }
+
+        .modal-buttons button {
+            padding: 0.625rem 1.5rem;
+            font-size: 0.95rem;
+        }
+
+        .modal-cancel {
+            background-color: #e2e8f0;
+            color: #2d3748;
+        }
+
+        .modal-cancel:hover {
+            background-color: #cbd5e0;
+        }
+
+        .modal-confirm {
+            background-color: #e53e3e;
+        }
+
+        .modal-confirm:hover {
+            background-color: #c53030;
+        }
     </style>
     <script>
         document.addEventListener('DOMContentLoaded', () => {
@@ -189,6 +270,9 @@
             const deleteButton = document.querySelector('.delete-button');
             const spinner = document.querySelector('.spinner');
             const message = document.querySelector('.message');
+            const deleteModal = document.getElementById('deleteModal');
+            const modalCancel = document.getElementById('modalCancel');
+            const modalConfirm = document.getElementById('modalConfirm');
 
             const showMessage = (text, type) => {
                 message.textContent = text;
@@ -199,6 +283,38 @@
                 }, 5000);
             };
 
+            const showDeleteModal = () => {
+                return new Promise((resolve) => {
+                    deleteModal.classList.add('active');
+
+                    const handleConfirm = () => {
+                        deleteModal.classList.remove('active');
+                        modalConfirm.removeEventListener('click', handleConfirm);
+                        modalCancel.removeEventListener('click', handleCancel);
+                        deleteModal.removeEventListener('click', handleOverlayClick);
+                        resolve(true);
+                    };
+
+                    const handleCancel = () => {
+                        deleteModal.classList.remove('active');
+                        modalConfirm.removeEventListener('click', handleConfirm);
+                        modalCancel.removeEventListener('click', handleCancel);
+                        deleteModal.removeEventListener('click', handleOverlayClick);
+                        resolve(false);
+                    };
+
+                    const handleOverlayClick = (e) => {
+                        if (e.target === deleteModal) {
+                            handleCancel();
+                        }
+                    };
+
+                    modalConfirm.addEventListener('click', handleConfirm);
+                    modalCancel.addEventListener('click', handleCancel);
+                    deleteModal.addEventListener('click', handleOverlayClick);
+                });
+            };
+
             inputs.forEach((input, index) => {
                 input.addEventListener('input', (e) => {
                     const value = e.target.value.toUpperCase().replace(/[^A-Z0-9]/g, '');
@@ -243,7 +359,8 @@
                     return;
                 }
 
-                if (!confirm('Are you sure you want to delete this file? This action cannot be undone.')) {
+                const confirmed = await showDeleteModal();
+                if (!confirmed) {
                     return;
                 }
 
@@ -351,5 +468,16 @@
         </form>
     </div>
     <div class="version">v{{ version }}</div>
+
+    <div class="modal-overlay" id="deleteModal">
+        <div class="modal">
+            <h2>Delete File</h2>
+            <p>Are you sure you want to delete this file? This action cannot be undone.</p>
+            <div class="modal-buttons">
+                <button type="button" class="modal-cancel" id="modalCancel">Cancel</button>
+                <button type="button" class="modal-confirm" id="modalConfirm">Delete</button>
+            </div>
+        </div>
+    </div>
 </body>
 </html>