refactor(whatsrust): relocate forwarding result types

[Andiveli]

Summary

• Relocate ForwardReport and ForwardFailure to the message-send owner.
• Preserve the public facade names and representations.

Changes

• Added forwarding result types and helper implementation to message_send.rs.
• Added explicit public facade reexports.

Chain Context

• Immediate parent: PR refactor(whatsrust): extract group and chat queries #327.
• Diagram: refactor(whatsrust): extract action wrappers #315 -> refactor(whatsrust): extract read synchronization wrappers #317 -> refactor(whatsrust): extract message payload builders #321 -> refactor(whatsrust): extract outbound message wrappers #324 -> refactor(whatsrust): extract contacts and communities queries #325 -> refactor(whatsrust): extract group and chat queries #327 -> 📍 this PR -> final facade cleanup.

Testing

• cargo fmt --all -- --check
• CARGO_TARGET_DIR=/home/samael/Escritorio/public/wptui-public/target cargo check --workspace --all-targets
• CARGO_TARGET_DIR=/home/samael/Escritorio/public/wptui-public/target cargo test -p whatsrust --lib -- --test-threads=1
• git diff --check

Review Budget and Rollback

• Authored diff: 63 lines (32 additions + 31 deletions).
• Rollback: revert commit f30fb97.

Closes #329

[Andiveli]

Superseded by repaired replacement PR; this branch was accidentally advanced with the final facade slice and is closed without rewriting history.