fix: disable Tauri native drag-drop to restore BlockNote block dragging

Tauri's default dragDropEnabled=true intercepts HTML5 DnD events at the
webview level, preventing BlockNote's block handle drag-to-reorder from
receiving dragstart/dragover/drop events. Setting dragDropEnabled=false
lets all drag events flow through standard HTML5 DnD, which BlockNote
expects.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/tauri.conf.json

@@ -22,7 +22,8 @@
         "fullscreen": false,
         "titleBarStyle": "Overlay",
         "hiddenTitle": true,
-        "backgroundColor": "#F7F6F3"
+        "backgroundColor": "#F7F6F3",
+        "dragDropEnabled": false
       }
     ],
     "security": {