fix: remove unused CSS classes, replace deprecated color tokens

Author: julhoang

static/css/v3/header.css

@@ -28,7 +28,6 @@
 .header__search-bar,
 .header__utilities-latest,
 .header__icon-btn,
-.header__mobile-logo,
 .header__menu-btn,
 .header__drawer-nav,
 .header__nav-btn,
@@ -69,8 +68,7 @@
   border-radius: var(--border-radius-m);
 }
 
-.header__logo img,
-.header__mobile-logo img {
+.header__logo img {
   width: 31px;
   height: 31px;
   display: block;
@@ -84,7 +82,7 @@
   color: var(--color-text-primary);
   text-decoration: none;
   font-size: var(--font-size-small);
-  font-weight: 400;
+  font-weight: var(--font-weight-regular);
   font-family: var(--font-sans);
   line-height: var(--line-height-relaxed);
   letter-spacing: var(--letter-spacing-tight);
@@ -107,7 +105,7 @@
 /* ── Selected ──────────────────────────────────── */
 
 .header__nav-link--active {
-  text-decoration: underline !important;
+  text-decoration: underline;
 }
 
 /* ── Unread (notification dot) ─────────────────── */
@@ -333,7 +331,7 @@ html.dark .header__icon--theme-moon {
 .header__user-trigger > .avatar {
   width: 100%;
   height: 100%;
-  display: block;
+  display: flex;
   border-radius: calc(var(--header-radius) - 2px);
   pointer-events: none;
 }
@@ -348,8 +346,8 @@ html.dark .header__icon--theme-moon {
   padding: var(--space-default) var(--space-medium);
   gap: var(--space-s);
   border-radius: var(--header-radius);
-  border: 1px solid var(--color-border);
-  background: var(--color-bg-secondary);
+  border: 1px solid var(--color-stroke-mid);
+  background: var(--color-surface-weak);
   z-index: 1000;
 }
 
@@ -372,14 +370,6 @@ html.dark .header__icon--theme-moon {
   gap: var(--space-s);
 }
 
-.header__mobile-logo {
-  display: flex;
-  flex-shrink: 0;
-  align-items: center;
-  justify-content: center;
-  padding: 0 var(--space-large);
-}
-
 .header__menu-btn {
   display: inline-flex;
   align-items: center;