fix(recipe): prevent empty grid by removing preserveScroll from refresh triggers

Bug: when scrolling down on recipes page, any operation with
preserveScroll: true would fetch only page 1 data then restore
scroll position to beyond the loaded items, leaving the grid empty.

Fix:
- Remove preserveScroll: true from all 7 must-refresh trigger
  paths (filter, search, sort, import, settings reload, sync,
  rebuild cache, sidebar folder nav)
- Replace full list refresh with updateSingleItem() for repair
  and bulk missing-LoRA download operations
- Update tests to match new scroll-free behavior

static/js/recipes.js

@@ -19,7 +19,7 @@ class RecipePageControls {
     }
 
     async resetAndReload() {
-        await refreshVirtualScroll({ preserveScroll: true });
+        await refreshVirtualScroll();
     }
 
     async refreshModels(fullRebuild = false) {