fix: propagate real message IDs via SSE and fix regenerate model parameter

- Add message_id and user_message_id to SSE done events so frontend
  can replace temp IDs with real DB IDs, fixing "消息不存在" on regenerate
- Replace Body(default=None) with RegenerateRequest Pydantic model for
  proper JSON body parsing, fixing 422 Unprocessable Content
- Frontend always sends model in regenerate request body
- Pass selected model through message-item → regenerateMessage chain
- Various UI refinements to chat sidebar, quick questions, and layout

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/src/app/(main)/chat/page.tsx

@@ -8,12 +8,15 @@ import ChatInterface from "@/components/chat/chat-interface";
 import Sidebar from "@/components/chat/sidebar";
 import MobileNav from "@/components/layout/mobile-nav";
 import LoadingSpinner from "@/components/ui/loading-spinner";
+import { Button } from "@/components/ui/button";
+import { PanelLeftClose, PanelLeftOpen } from "lucide-react";
 
 export default function ChatPage() {
   const router = useRouter();
   const { isAuthenticated, user, isLoading: authLoading } = useAuthStore();
   const { loadSessions, isLoading: chatLoading } = useChatStore();
   const [isInitialized, setIsInitialized] = useState(false);
+  const [sidebarOpen, setSidebarOpen] = useState(true);
 
   useEffect(() => {
     if (!authLoading && !isAuthenticated) {
@@ -22,7 +25,6 @@ export default function ChatPage() {
     }
 
     if (isAuthenticated && !isInitialized) {
-      // 加载聊天会话
       loadSessions();
       setIsInitialized(true);
     }
@@ -41,18 +43,45 @@ export default function ChatPage() {
   }
 
   return (
-    <div className="h-[calc(100vh-4rem)] bg-background flex">
-      {/* 侧边栏 */}
-      <div className="w-80 border-r bg-card/50 flex-shrink-0">
-        <Sidebar />
-      </div>
-      
-      {/* 主聊天区域 */}
-      <div className="flex-1 flex flex-col min-w-0">
-        <ChatInterface />
+    <div className="h-[calc(100vh-4rem)] bg-background">
+      <div className="h-full max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 flex gap-4 py-4">
+        {/* Mobile overlay */}
+        {sidebarOpen && (
+          <div
+            className="fixed inset-0 bg-black/30 z-30 md:hidden"
+            onClick={() => setSidebarOpen(false)}
+          />
+        )}
+
+        {/* Sidebar — persistent on desktop, overlay on mobile */}
+        <div className={`
+          shrink-0 z-40
+          w-[260px] rounded-xl border border-border/40 bg-card shadow-sm
+          transition-all duration-200 ease-in-out overflow-hidden
+          fixed md:relative md:top-auto md:left-auto md:bottom-auto
+          ${sidebarOpen ? 'translate-x-0' : '-translate-x-full md:hidden'}
+        `}>
+          <Sidebar onClose={() => setSidebarOpen(false)} />
+        </div>
+
+        {/* Main chat area */}
+        <div className="flex-1 flex flex-col min-w-0 relative rounded-xl border border-border/40 bg-card shadow-sm overflow-hidden">
+          {/* Toggle button */}
+          {!sidebarOpen && (
+            <Button
+              variant="ghost"
+              size="icon"
+              onClick={() => setSidebarOpen(true)}
+              className="absolute top-3 left-3 z-10 h-9 w-9 text-muted-foreground hover:text-foreground hover:bg-muted/50"
+            >
+              <PanelLeftOpen className="w-5 h-5" />
+            </Button>
+          )}
+
+          <ChatInterface />
+        </div>
       </div>
 
-      {/* 移动端导航 */}
       <MobileNav />
     </div>
   );