Add edit button to sidebar items and fix initial terminal fit

- Add pencil edit button on each sidebar profile item (visible on hover)
- Fire fitAddon.fit() multiple times after terminal creation (50/150/400ms)
  to catch the panel finishing its CSS layout
- Re-fit terminal when session:state transitions to 'connected'

frontend/src/css/sidebar.css

@@ -212,6 +212,33 @@
     margin-top: 1px;
 }
 
+/* Edit button (appears on hover, beside name) */
+.sidebar-item-edit {
+    flex-shrink: 0;
+    width: 22px;
+    height: 22px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    font-size: 12px;
+    color: var(--text-disabled);
+    background: none;
+    border: none;
+    border-radius: var(--radius-sm);
+    cursor: pointer;
+    opacity: 0;
+    transition: opacity var(--transition-fast), color var(--transition-fast), background var(--transition-fast);
+}
+
+.sidebar-item:hover .sidebar-item-edit {
+    opacity: 1;
+}
+
+.sidebar-item-edit:hover {
+    color: var(--accent);
+    background: var(--bg-hover);
+}
+
 /* Favourite star */
 .sidebar-item-star {
     flex-shrink: 0;