style(ui): redesign app layout to native macOS density and refine visual theme

- Adjusted overall layout scale to perfectly match original native macOS density.

- Refined sidebar into a floating rounded slab with proper padding, border, and toggle button placement.

- Fixed drag region overlap preventing button interactions in the title bar.

- Removed artificial shadow lines and scrollbars from the sidebar.

- Updated Tauri backend configuration, dependencies, and scheduler functions for improved stability.

apps/desktop/src-tauri/tauri.conf.json

@@ -18,12 +18,14 @@
         "minWidth": 800,
         "minHeight": 600,
         "titleBarStyle": "Overlay",
-        "hiddenTitle": true
+        "hiddenTitle": true,
+        "transparent": true
       }
     ],
     "security": {
       "csp": null
-    }
+    },
+    "macOSPrivateApi": true
   },
   "bundle": {
     "active": true,