style: Update z-index for theme switcher and topbar; add custom scrollbar styles

public/styles/components/themebutton.css

@@ -11,7 +11,7 @@
   display: flex;
   align-items: center;
   gap: 8px;
-  z-index: 1000;
+  z-index: 1050;
 }
 
 .theme-switcher label {

public/styles/layout/topbar.css

@@ -3,6 +3,10 @@
   align-items: center;
   justify-content: space-between;
 
+  position: fixed;
+  top: 0;
+  z-index: 1100;
+
   height: 48px;
   width: 100%;
 

public/styles/styles.css

@@ -49,6 +49,47 @@ body {
 
 }
 
+/* Scrollbar globale pour Chromium/Electron */
+body::-webkit-scrollbar {
+  width: 10px;
+  height: 10px;
+}
+
+body::-webkit-scrollbar-track {
+  background: rgba(255, 255, 255, 0.03);
+  border-radius: 5px;
+}
+
+body::-webkit-scrollbar-thumb {
+  background-color: rgba(255, 255, 255, 0.2);
+  border-radius: 5px;
+  border: 2px solid transparent;
+  background-clip: padding-box;
+  transition: background-color 0.2s ease, transform 0.2s ease;
+}
+
+body::-webkit-scrollbar-thumb:hover {
+  background-color: rgba(255, 255, 255, 0.35);
+  transform: scaleX(1.05);
+}
+
+/* Thème clair */
+body.light::-webkit-scrollbar-track {
+  background: rgba(0, 0, 0, 0.05);
+}
+
+body.light::-webkit-scrollbar-thumb {
+  background-color: rgba(0, 0, 0, 0.25);
+}
+
+body.light::-webkit-scrollbar-thumb:hover {
+  background-color: rgba(0, 0, 0, 0.45);
+}
+
+.container{
+  margin-top: 50px;
+}
+
 header p{
   color: var(--subtitle-color);
 }