Sidebar mobile improvement

The sidebar vanished on a too small display. Button to reopen and close
are rendered

frontend/src/styles/components/_sidebar.scss

@@ -49,9 +49,50 @@
     text-align: left;
   }
 
-  .home {
+  .sidebar-header {
     display: flex;
-    justify-content: center;
+    align-items: center;
+    justify-content: space-between;
+    width: 100%;
+    margin-bottom: $spacing-md;
+
+    .home {
+      flex-grow: 1;
+      display: flex;
+      justify-content: center;
+      
+      @media (max-width: 768px) {
+        padding-left: 36px;
+      }
+    }
+
+    .sidebar-close {
+      display: none;
+      background: transparent;
+      border: none;
+      color: #fff;
+      cursor: pointer;
+      padding: 8px;
+      border-radius: 50%;
+      align-items: center;
+      justify-content: center;
+      transition: background 0.2s ease-in-out;
+      margin-bottom: 0;
+
+      &:hover {
+        background: rgba(255, 255, 255, 0.1);
+      }
+
+      svg {
+        width: 20px;
+        height: 20px;
+        stroke: #fff;
+      }
+
+      @media (max-width: 768px) {
+        display: flex;
+      }
+    }
   }
   
   .home-svg {
@@ -64,3 +105,70 @@
   &.user { width: 220px; background: darken($color-sidebar, 6%); }
 }
 
+// Floating mobile menu toggle button
+.mobile-menu-toggle {
+  display: none;
+  
+  @media (max-width: 768px) {
+    display: flex;
+    position: fixed;
+    top: 1rem;
+    left: 1rem;
+    z-index: 998;
+    width: 48px;
+    height: 48px;
+    border-radius: 50%;
+    border: 1px solid rgba(128, 128, 128, 0.2);
+    background-color: var(--color-container);
+    color: var(--color-text);
+    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
+    cursor: pointer;
+    align-items: center;
+    justify-content: center;
+    padding: 0;
+    transition: all 0.2s ease-in-out;
+    
+    svg {
+      width: 24px;
+      height: 24px;
+      stroke: var(--color-text);
+      transition: stroke 0.2s ease-in-out;
+    }
+    
+    &:hover {
+      transform: translateY(-1px);
+      box-shadow: 0 6px 16px rgba(0, 0, 0, 0.2);
+      background-color: var(--color-bg);
+    }
+    
+    &:active {
+      transform: translateY(0);
+    }
+  }
+}
+
+// Overlay backdrop that dims the screen and allows dismissals on mobile
+.sidebar-overlay {
+  display: none;
+  
+  @media (max-width: 768px) {
+    display: block;
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100vw;
+    height: 100vh;
+    background: rgba(0, 0, 0, 0.4);
+    backdrop-filter: blur(4px);
+    z-index: 999;
+    opacity: 0;
+    pointer-events: none;
+    transition: opacity 0.3s ease-in-out;
+    
+    &.open {
+      opacity: 1;
+      pointer-events: auto;
+    }
+  }
+}
+