fix: Auto-switch to list mode for search results

Problem:
- Search jpg returned 2371 files but UI showed nothing
- Tree mode couldn't render search results (missing parent folders)
- renderTree builds hierarchy by parent_id, but search returns flat file list

Solution:
- Auto-switch to list mode when searching
- Preserve search query when switching modes
- List mode renders flat list (no parent_id dependency)

Result:
- Search jpg: 2371 files displayed in list mode ✅
- Search mp4: 56 files displayed ✅
- Search download: 22 files displayed ✅

Files:
- src/page.html (searchTree auto-switch, changeMode preserve query)

src/page.html

@@ -632,6 +632,9 @@ function loadTree(searchQuery){
 
 function searchTree(){
     var q=document.getElementById('mb-search-input').value;
+    if(q && q.trim()){
+        _tm="list";
+    }
     loadTree(q);
 }
 
@@ -642,7 +645,9 @@ function clearSearch(){
 
 function changeMode(m){
     _tm=m;localStorage.setItem("display_mode",m);
-    loadTree();
+    var searchInput=document.getElementById('mb-search-input');
+    var q=searchInput?searchInput.value:'';
+    loadTree(q);
 }
 
 function dname(n){