feat(UI): Adding a session manager (#3203)

# What does this PR do?

- Introduces the Agent Session creation for the Playground and allows
users to set tools
- note tools are actually not usable yet and this is marked explicitly
- this also caches sessions locally for faster loading on the UI and
deletes them appropriately
   - allows users to easily create new sessions as well
- Moved Model Configuration settings and "System Message" / Prompt to
the left component
- Added new logo and favicon
- Added new typing animation when LLM is generating

### Create New Session
<img width="1916" height="1393" alt="Screenshot 2025-08-21 at 4 18
08 PM"
src="https://github.com/user-attachments/assets/52c70ae3-a33e-4338-8522-8184c692c320"
/>


### List of Sessions
<img width="1920" height="1391" alt="Screenshot 2025-08-21 at 4 18
56 PM"
src="https://github.com/user-attachments/assets/ed78c3c6-08ec-486c-8bad-9b7382c11360"
/>

<!-- If resolving an issue, uncomment and update the line below -->
<!-- Closes #[issue-number] -->

## Test Plan
Unit tests added

---------

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

llama_stack/ui/app/layout.tsx

@@ -18,6 +18,9 @@ const geistMono = Geist_Mono({
 export const metadata: Metadata = {
   title: "Llama Stack",
   description: "Llama Stack UI",
+  icons: {
+    icon: "/favicon.ico",
+  },
 };
 
 import { SidebarProvider, SidebarTrigger } from "@/components/ui/sidebar";