feat: 新增深色模式支持；修复已知问题；样式优化

web/src/assets/styles/element/index.scss

@@ -0,0 +1,17 @@
+/*just override what you need*/
+@forward 'element-plus/theme-chalk/src/dark/var.scss' with (
+  $bg-color: (
+    'page': #0a0a0a,
+    '': #141414,
+    'overlay': #1d1e1f,
+  ),
+  $fill-color: (
+    '': #262727,
+    'light': #1d1e1f,
+    'lighter': #141414,
+    'extra-light': #191919,
+    'dark': #3a3a3a,
+    'darker': #4a4a4a,
+    'blank': #1a1a1a,
+  )
+);