[DASH-540] Nebula - Various UI improvements (#5777)

## Problem solved

DASH-540

* on the chat page -> move the container 1 level down - so the chat can be scrolled from the corner of the page as well
* reduce container max-width for the history page to 800px to match it with landing page
* stop the auto scroll if user interacts with chat UI
* custom 404 page for the nebula subdomain
* remove the announcement banner from the 404 pages ( this affects entire dashboard)
* fix empty title in chat history page
* fix overflow in chat history page on mobile when there's a long text without a whitespace

<!-- start pr-codex -->

---

## PR-Codex overview
This PR focuses on enhancing the chat functionality and user experience in the `Nebula` application. It introduces auto-scrolling features, improves layout styling, and adds a new `404 Not Found` page.

### Detailed summary
- Added auto-scrolling feature to `Chats` component.
- Introduced `setEnableAutoScroll` function to manage scrolling behavior.
- Enhanced styling in `ChatHistoryPage` and `SessionCard`.
- Implemented a new `NebulaNotFound` component with a user-friendly 404 message.
- Updated `ChatPageContent` to utilize the new auto-scroll functionality.

> ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your question}`

<!-- end pr-codex -->

Author: MananTank

apps/dashboard/src/app/nebula-app/(app)/chat/history/ChatHistoryPage.tsx

@@ -81,12 +81,12 @@ export function ChatHistoryPageUI(props: {
 
       {filteredSessions.length > 0 && (
         <ScrollShadow
-          className="container flex-1"
+          className="container max-w-[800px] flex-1"
           scrollableClassName="max-h-full py-6"
           shadowColor="hsl(var(--background))"
         >
           {filteredSessions.length > 0 && (
-            <div className="flex flex-col gap-4">
+            <div className="flex flex-col gap-5">
               {filteredSessions.map((session) => (
                 <SessionCard
                   key={session.id + session.updated_at + session.created_at}
@@ -175,8 +175,10 @@ function SessionCard(props: {
   });
 
   return (
-    <div className="rounded-lg border bg-muted/50 p-4">
-      <h3>{props.session.title}</h3>
+    <div className="overflow-hidden rounded-lg border bg-muted/50 p-4">
+      <h3 className="line-clamp-3 break-all">
+        {props.session.title || "Untitled"}
+      </h3>
       <div className="mt-4 flex items-center justify-between gap-6 border-t pt-3">
         <p className="text-muted-foreground text-sm">
           Updated{" "}

apps/dashboard/src/app/nebula-app/(app)/components/ChatPageContent.tsx

@@ -1,7 +1,4 @@
 "use client";
-
-/* eslint-disable no-restricted-syntax */
-import { ScrollShadow } from "@/components/ui/ScrollShadow/ScrollShadow";
 import { useThirdwebClient } from "@/constants/thirdweb.client";
 import type { Account } from "@3rdweb-sdk/react/hooks/useApi";
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
@@ -111,18 +108,8 @@ export function ChatPageContent(props: {
     [props.type],
   );
 
-  const messagesEndRef = useRef<HTMLDivElement>(null);
   const [isChatStreaming, setIsChatStreaming] = useState(false);
-  const [isUserSubmittedMessage, setIsUserSubmittedMessage] = useState(false);
-
-  // biome-ignore lint/correctness/useExhaustiveDependencies: <explanation>
-  useEffect(() => {
-    if (!isUserSubmittedMessage) {
-      return;
-    }
-
-    messagesEndRef.current?.scrollIntoView({ behavior: "smooth" });
-  }, [messages, isUserSubmittedMessage]);
+  const [enableAutoScroll, setEnableAutoScroll] = useState(false);
 
   const initSession = useCallback(async () => {
     const session = await createSession({
@@ -148,7 +135,7 @@ export function ChatPageContent(props: {
       ]);
 
       setIsChatStreaming(true);
-      setIsUserSubmittedMessage(true);
+      setEnableAutoScroll(true);
       const abortController = new AbortController();
 
       try {
@@ -292,6 +279,7 @@ export function ChatPageContent(props: {
         });
       } finally {
         setIsChatStreaming(false);
+        setEnableAutoScroll(false);
       }
     },
     [
@@ -305,6 +293,8 @@ export function ChatPageContent(props: {
   );
 
   const hasDoneAutoPrompt = useRef(false);
+
+  // eslint-disable-next-line no-restricted-syntax
   useEffect(() => {
     if (
       props.initialPrompt &&
@@ -337,45 +327,40 @@ export function ChatPageContent(props: {
           }}
         />
       </header>
-      <div className="container relative flex max-w-[800px] grow flex-col overflow-hidden rounded-lg pb-6">
+      <div className="relative flex grow flex-col overflow-hidden rounded-lg pb-6">
         {showEmptyState ? (
-          <div className="fade-in-0 flex grow animate-in flex-col justify-center">
+          <div className="fade-in-0 container flex max-w-[800px] grow animate-in flex-col justify-center">
             <EmptyStateChatPageContent sendMessage={handleSendMessage} />
           </div>
         ) : (
           <div className="fade-in-0 relative z-[0] flex max-h-full flex-1 animate-in flex-col overflow-hidden">
-            <ScrollShadow
-              className="flex-1"
-              scrollableClassName="max-h-full"
-              shadowColor="hsl(var(--background))"
-              shadowClassName="z-[1]"
-            >
-              <Chats
-                messages={messages}
-                isChatStreaming={isChatStreaming}
-                authToken={props.authToken}
-                sessionId={sessionId}
-                className="min-w-0 pt-10 pb-32"
-                twAccount={props.account}
-                client={client}
-              />
-              {/* Scroll anchor */}
-              <div ref={messagesEndRef} />
-            </ScrollShadow>
-
-            <Chatbar
-              sendMessage={handleSendMessage}
+            <Chats
+              messages={messages}
               isChatStreaming={isChatStreaming}
-              abortChatStream={() => {
-                chatAbortController?.abort();
-                setChatAbortController(undefined);
-                setIsChatStreaming(false);
-                // if last message is presence, remove it
-                if (messages[messages.length - 1]?.type === "presence") {
-                  setMessages((prev) => prev.slice(0, -1));
-                }
-              }}
+              authToken={props.authToken}
+              sessionId={sessionId}
+              className="min-w-0 pt-10 pb-32"
+              twAccount={props.account}
+              client={client}
+              enableAutoScroll={enableAutoScroll}
+              setEnableAutoScroll={setEnableAutoScroll}
             />
+
+            <div className="container max-w-[800px]">
+              <Chatbar
+                sendMessage={handleSendMessage}
+                isChatStreaming={isChatStreaming}
+                abortChatStream={() => {
+                  chatAbortController?.abort();
+                  setChatAbortController(undefined);
+                  setIsChatStreaming(false);
+                  // if last message is presence, remove it
+                  if (messages[messages.length - 1]?.type === "presence") {
+                    setMessages((prev) => prev.slice(0, -1));
+                  }
+                }}
+              />
+            </div>
           </div>
         )}
 

apps/dashboard/src/app/nebula-app/(app)/components/Chats.stories.tsx

@@ -157,6 +157,8 @@ function Story() {
             },
           ]}
           client={getThirdwebClient()}
+          enableAutoScroll={true}
+          setEnableAutoScroll={() => {}}
         />
       </BadgeContainer>
 
@@ -167,6 +169,8 @@ function Story() {
           isChatStreaming={false}
           sessionId="xxxxx"
           twAccount={accountStub()}
+          enableAutoScroll={true}
+          setEnableAutoScroll={() => {}}
           messages={[
             {
               text: randomLorem(10),
@@ -182,6 +186,8 @@ function Story() {
 
       <BadgeContainer label="User + Assistant responses">
         <Chats
+          enableAutoScroll={true}
+          setEnableAutoScroll={() => {}}
           client={getThirdwebClient()}
           authToken="xxxxx"
           isChatStreaming={false}