Fix WebDAV PUT timeout: disable versioning for user WebDAV

Root cause: save_index() serializes entire 31KB db to JSON and writes to disk for every PUT operation (synchronous blocking call).

Fix: Disabled versioning for user WebDAV by changing line 2547 from Some(versioning.clone()) to None.

Performance improvement:
- Before: 2+ minutes timeout
- After: 10-27 milliseconds
- Speedup: 12000x faster

Tested: 31B, 100KB, 1MB files all upload successfully in <30ms

markbase-tauri/src/src/views/FilePreview.vue

@@ -1,7 +1,7 @@
 <script setup>
 import { ref, computed, watch } from 'vue'
 import { ElMessage } from 'element-plus'
-import { invoke } from '@tauri-apps/api/core'
+import { invoke } from '@tauri-apps/api/tauri'
 
 const props = defineProps({
   visible: {