style: dark mobile UI — bottom nav + topbar match sidebar

- Mobile bottom nav: white → dark (#1c1c1e) bg, white icons/text
- Mobile topbar: white → dark bg on small screens, white text/controls
- Mobile logo color: dark → white for dark bg readability
- Desktop topbar remains white (contrasts with dark sidebar)

static/yaris.css

@@ -190,10 +190,10 @@ body {
     left: 0;
     right: 0;
     height: 3.75rem;
-    background: #fff;
-    border-top: 1px solid rgba(0,0,0,.1);
+    background: var(--sidebar-bg);
+    border-top: 1px solid rgba(255,255,255,.1);
     z-index: 1040;
-    box-shadow: 0 -2px 8px rgba(0,0,0,.08);
+    box-shadow: 0 -2px 8px rgba(0,0,0,.3);
 }
 
 .mobile-nav-item {
@@ -203,7 +203,7 @@ body {
     align-items: center;
     justify-content: center;
     gap: .2rem;
-    color: #6c757d;
+    color: rgba(255,255,255,.55);
     text-decoration: none;
     font-size: .6rem;
     font-weight: 500;
@@ -218,17 +218,39 @@ body {
 }
 
 .mobile-nav-item.active {
-    color: var(--primary);
+    color: #fff;
 }
 
 .mobile-nav-item:hover {
-    color: var(--primary);
+    color: rgba(255,255,255,.85);
 }
 
+/* Mobile: dark topbar (no sidebar on mobile, so topbar acts as the header) */
 @media (max-width: 767.98px) {
     #content-wrapper {
         margin-left: 0 !important;
     }
+    .topbar {
+        background: var(--sidebar-bg) !important;
+        border-bottom: 1px solid rgba(255,255,255,.1);
+        color: #fff;
+    }
+    .topbar .navbar-brand,
+    .topbar .text-muted,
+    .topbar .btn-outline-secondary {
+        color: rgba(255,255,255,.85) !important;
+        border-color: rgba(255,255,255,.25);
+    }
+    .topbar .btn-outline-secondary:hover {
+        background: rgba(255,255,255,.1);
+        color: #fff !important;
+    }
+    .topbar .fa-bell { color: rgba(255,255,255,.7) !important; }
+    .topbar .form-select-sm {
+        background-color: rgba(255,255,255,.1);
+        border-color: rgba(255,255,255,.2);
+        color: #fff;
+    }
     .main-content {
         padding-bottom: 7rem;
     }