Splice APIs:  add more tiles to the API Reference landing page

Need to add the following items API Reference landing page:
- Splice APIs
- dApp API
- Wallet Gateway
- Admin API 


From 

<img width="1253" height="860" alt="Image" src="https://github.com/user-attachments/assets/ad45fe77-e64a-4aff-ab27-0521ce6f4fc0" />

To

<img width="874" height="1190" alt="Image" src="https://github.com/user-attachments/assets/c0e40755-1e14-4696-a90b-3caf08ad3025" />
