Implement Client-Side Decorations (CSD) with custom title bar

- Disable native window decorations in tauri.conf.json
- Create TitleBar component with minimize/maximize/close controls
- Add drag region for window movement
- Integrate TitleBar into main layout and LoginView
- Adjust content heights to account for 36px title bar
- Prepare for future mini player implementation

src-tauri/tauri.conf.json

@@ -17,7 +17,7 @@
         "height": 800,
         "minWidth": 800,
         "minHeight": 600,
-        "decorations": true,
+        "decorations": false,
         "transparent": false,
         "resizable": true
       }