refactor(style): update chat layout and scrolling

frontend/src/components/chatSidebarStore.ts

@@ -0,0 +1,24 @@
+import Alpine from 'alpinejs';
+
+const COLLAPSED_KEY = 'aethera-chat-sidebar-collapsed';
+
+interface ChatSidebarStore {
+  mobileOpen: boolean;
+  collapsed: boolean;
+  toggleMobile(): void;
+  toggleCollapsed(): void;
+}
+
+const store: ChatSidebarStore = {
+  mobileOpen: false,
+  collapsed: localStorage.getItem(COLLAPSED_KEY) === 'true',
+  toggleMobile() {
+    this.mobileOpen = !this.mobileOpen;
+  },
+  toggleCollapsed() {
+    this.collapsed = !this.collapsed;
+    localStorage.setItem(COLLAPSED_KEY, String(this.collapsed));
+  },
+};
+
+Alpine.store('chatSidebar', store);