Joshenlim/fe 4068 warn users ai assistant history can be wiped (#51260)

## Context

Chats with the AI Assistant is currently stored locally on the browser
and not synced across devices which caused a bit of confusion for some
users when they realised they couldn't access their chat histories on
different devices. (Ideal state tbh is to persist the chat
conversations, but that'll need support on the BE)

PR here just adds a foot note to both the chat history dropdown in the
side panel + chat nav for the explorer regarding this - opting for
something with a small footprint
<img width="293" height="322" alt="image"
src="https://github.com/user-attachments/assets/284ee0c1-16bf-432b-b473-29ee048ed4cc"
/>
<img width="392" height="956" alt="image"
src="https://github.com/user-attachments/assets/e5eb1409-fa63-4dae-9439-86facbe41277"
/>

---------

Co-authored-by: Gildas Garcia <1122076+djhi@users.noreply.github.com>

apps/studio/components/layouts/ExplorerLayout/ExplorerNavChats.tsx

@@ -55,6 +55,11 @@ export const ExplorerNavChats = () => {
           })
         )}
       </div>
+      <section className="flex shrink-0 flex-col gap-3 border-t border-default p-3">
+        <p className="text-xs text-foreground-lighter">
+          Chat history is saved to this browser and isn't synced across devices.
+        </p>
+      </section>
     </ExplorerNavResourceWrapper>
   )
 }

apps/studio/components/ui/AIAssistantPanel/AIAssistantChatSelector.tsx

@@ -222,6 +222,12 @@ export const AIAssistantChatSelector = ({
                 <span>Start a new chat</span>
               </CommandItem>
             </CommandGroup>
+            <CommandSeparator />
+            <CommandGroup className="px-2 py-1.5">
+              <p className="text-xs text-foreground-lighter">
+                Chat history is saved to this browser and isn't synced across devices.
+              </p>
+            </CommandGroup>
           </CommandList>
         </Command>
       </PopoverContent>