Change transaction's size to support low connection

### Is your feature request related to a problem?

Some nodes don't have a good latency, for now we are using 3MB as content's data of the transaction's structure to support websites, etc.
But this is not scalable for multi nodes communication, etc.

### Describe the solution you'd like

The proposal is to reduce the size of the transaction to 256KB to be more standardized as other decentralized protocols, allowing to have better bandwidth saving for multi nodes communication and transactions.

### Additional context

This change should have a direct impact on the aeweb sdk implementations and required new implementations.
New websites deployed with aeweb using older version will not be accepted after this change.

### Epic

_No response_

The issue names no files or tests. Start by tracing how the transaction's current 3MB limit is defined and used, then review the aeweb SDK implementations and compatibility impact; done means enforcing the proposed 256KB size without accepting incompatible older deployments.

Written by the indexing model from the issue text.