style(fe): optimize sidebar width to 200px and collapse width to 44px with clean toggle header

frontend/src/shared/shell/KsSidebar.vue

@@ -133,13 +133,15 @@ const sidebarClass = computed(() => ({
   <aside aria-label="주요 메뉴" :class="['ks-sidebar', sidebarClass]">
     <!-- Header with collapse button -->
     <div class="ks-sidebar__header">
+      <span v-if="!collapsed" class="ks-sidebar__title">주요 메뉴</span>
       <button
         type="button"
         class="ks-sidebar__collapse-btn"
-        :aria-label="collapsed ? '사이드바 펴기' : '사이드바 접기'"
+        :title="collapsed ? '메뉴 펼치기' : '메뉴 접기'"
+        :aria-label="collapsed ? '메뉴 펼치기' : '메뉴 접기'"
         @click="handleToggleCollapse"
       >
-        {{ collapsed ? '›' : '‹' }}
+        {{ collapsed ? '▶' : '◀ 접기' }}
       </button>
     </div>
 
@@ -212,41 +214,52 @@ const sidebarClass = computed(() => ({
 
 <style scoped>
 .ks-sidebar {
-  width: 280px;
+  width: var(--ks-shell-sidebar-width, 200px);
   background-color: var(--color-background-secondary);
   border-right: 1px solid var(--color-border-primary);
   display: flex;
   flex-direction: column;
-  transition: width 300ms cubic-bezier(0.4, 0, 0.2, 1);
+  transition: width 200ms cubic-bezier(0.4, 0, 0.2, 1);
   overflow-y: auto;
   overflow-x: hidden;
+  flex-shrink: 0;
 }
 
 .ks-sidebar--collapsed {
-  width: 80px;
+  width: var(--ks-shell-sidebar-collapsed, 44px);
 }
 
 .ks-sidebar__header {
-  padding: var(--spacing-4);
+  padding: var(--ks-space-2) var(--ks-space-3);
   border-bottom: 1px solid var(--color-border-primary);
   display: flex;
-  justify-content: flex-end;
+  align-items: center;
+  justify-content: space-between;
+  height: 38px;
+  box-sizing: border-border-box;
+}
+
+.ks-sidebar__title {
+  font-size: var(--ks-font-caption);
+  font-weight: 700;
+  color: var(--ks-color-text-muted);
+  letter-spacing: 0.05em;
+  text-transform: uppercase;
 }
 
 .ks-sidebar__collapse-btn {
-  background-color: var(--color-background-primary);
-  border: 1px solid var(--color-border-primary);
-  font-size: 24px;
+  background-color: transparent;
+  border: 1px solid var(--ks-color-border);
+  font-size: 11px;
   cursor: pointer;
-  color: var(--color-text-primary);
-  padding: var(--spacing-1);
-  border-radius: var(--border-radius-base);
-  transition: all var(--transition-base);
+  color: var(--ks-color-text-muted);
+  padding: 2px 6px;
+  border-radius: var(--ks-radius-sm);
+  transition: var(--ks-transition-fast);
   display: flex;
   align-items: center;
   justify-content: center;
-  width: 40px;
-  height: 40px;
+  height: 24px;
 }
 
 .ks-sidebar__collapse-btn:hover {