feat(explorer): add search by proof hash

[glpecile]

Changes

• add method to proofs API that returns the merkle root of the batch that contains proof hash hex
  • caveat: sometimes a proof hash is included in more than one batch, the returned value is the limited to the latest one ordered by id
• add method call to search live component
• edit placeholder text to include batch search

Demo

https://github.com/user-attachments/assets/6a7b6507-96df-44fe-a5e4-f57afa1fbe0e