fix(web): improve event polling

[JuArce]

This PR makes some changes to how the blocks are fetched:

• To keep a buffer of 10 blocks to avoid possible missing events.
• Makes public the fetch_logs to be called on the iex terminal when fetching the last N logs.
• Moves the claim counter increment to the proofs module update_proof_status_claimed method, to avoid having the increment call each time the claim status is set.

To fetch all events on devnet, you can use the following command on the iex terminal:

ZkArcade.SubmissionPoller.handle_info(:poll, %{from_block: 0})

Note that, since we are in devnet, we use the zero block, but in mainnet, we should fetch it from network.

[JuArce]

LGTM