feat: improve move dialog with folder navigation

- Remove 'Root' option from move dialog (users move within their home folder)
- Show children of current folder instead of flat folder list
- Add breadcrumb navigation for folder browsing
- Add 'go to parent' navigation option
- Add 'select this folder' option to choose current location
- Add CSS styles for new navigation elements
- Add dark mode support for move dialog
- Add i18n translations for new strings (en, es)

static/js/app/ui.js

@@ -102,7 +102,7 @@ const ui = {
             document.body.appendChild(renameDialog);
         }
 
-        // Move dialog — modern
+        // Move dialog — modern with navigation
         if (!document.getElementById('move-file-dialog')) {
             const moveDialog = document.createElement('div');
             moveDialog.className = 'rename-dialog';
@@ -115,10 +115,8 @@ const ui = {
                     </div>
                     <div class="rename-dialog-body">
                         <p style="margin:0 0 12px;color:#718096;font-size:14px" data-i18n="dialogs.select_destination">Select destination folder:</p>
+                        <div id="move-dialog-breadcrumb" class="move-dialog-breadcrumb"></div>
                         <div id="folder-select-container" style="max-height:220px;overflow-y:auto;">
-                            <div class="folder-select-item selected" data-folder-id="">
-                                <i class="fas fa-folder"></i> <span data-i18n="dialogs.root">Root</span>
-                            </div>
                         </div>
                     </div>
                     <div class="rename-dialog-buttons">