refactor(primitives): remove batch_hash from morph header

[panos-xyz]

Background

batch_hash is currently included in Morph block header.
Based on current architecture and usage, this field is no longer necessary and increases maintenance complexity.

Functional Description

Refactor header-related code to remove batch_hash completely.
Ensure payload building, execution, and RPC paths continue to work after this change.

Scope

• Remove batch_hash from Morph header definition
• Update all related references in payload / evm / rpc / node code
• Update affected tests and docs

Acceptance Criteria

• batch_hash is removed from Morph header and related structs
• cargo check --workspace passes
• Related tests pass
• Node can start and build blocks normally

Reference

• Design/Discussion:
• Related source file: crates/primitives/src/header.rs