Redesign sidebar user section to fix overlap issue

Restructured layout: avatar, truncated username, and logout icon
in a single row. Collapsed state stacks vertically. Logout button
uses a subtle icon-only style with red hover. Proper text ellipsis
prevents name overflow.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/main.css

@@ -300,6 +300,84 @@ tr:hover {
     color: var(--text-secondary);
 }
 
+/* Sidebar User Section */
+.sidebar-user {
+    display: flex;
+    align-items: center;
+    gap: 10px;
+    padding: 12px 14px;
+    margin: 8px;
+    border-top: 1px solid var(--border);
+    padding-top: 16px;
+}
+
+.sidebar-user-collapsed {
+    flex-direction: column;
+    gap: 8px;
+    padding: 12px 4px;
+    margin: 8px 4px;
+}
+
+.user-avatar {
+    width: 34px;
+    height: 34px;
+    border-radius: 10px;
+    background: linear-gradient(135deg, rgba(56, 189, 248, 0.2), rgba(56, 189, 248, 0.08));
+    border: 1px solid rgba(56, 189, 248, 0.15);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    flex-shrink: 0;
+}
+
+.avatar-initials {
+    font-size: 13px;
+    font-weight: 700;
+    color: var(--accent);
+    line-height: 1;
+}
+
+.avatar-img {
+    width: 100%;
+    height: 100%;
+    border-radius: 10px;
+    object-fit: cover;
+}
+
+.user-name {
+    flex: 1;
+    font-size: 13px;
+    font-weight: 500;
+    color: var(--text-primary);
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    min-width: 0;
+}
+
+.logout-btn {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    width: 32px;
+    height: 32px;
+    border-radius: 8px;
+    color: var(--text-secondary);
+    text-decoration: none;
+    flex-shrink: 0;
+    transition: all 0.15s;
+}
+
+.logout-btn:hover {
+    background: rgba(239, 68, 68, 0.12);
+    color: #fca5a5;
+}
+
+.logout-btn-collapsed {
+    width: 34px;
+    height: 34px;
+}
+
 @media (max-width: 768px) {
     .sidebar {
         transform: translateX(-100%);