refactor(whatsrust): extract lifecycle wrappers

[Andiveli]

Summary

• Extract the public client lifecycle wrappers from the whatsrust facade.
• Keep client creation, QR connection callback, disconnect, logout, and phone pairing behavior unchanged.

Changes

• Added whatsrust/src/lifecycle.rs.
• Re-exported new_client, connect, disconnect, logout, and pair_phone from lib.rs.
• Kept the callback translator and setup macro contract intact at the FFI boundary.

Chain Context

• Start: PR refactor(whatsrust): extract callback registrations #311 (refactor/whatsrust-callback-registrations).
• End: lifecycle wrappers isolated; presence, media, and action slices remain.
• Dependency: this PR is the immediate parent for the presence slice.
• Diagram: #301 -> #311 -> 📍 #312 -> #313 -> #314 -> #315.
• Deferred: Cargo compilation/tests are intentionally deferred per task instructions; only formatting/source/diff checks were run.
• Rollback: revert commit 235b3ba / remove lifecycle.rs and restore these wrappers in lib.rs; no unrelated behavior changes.

Testing

• cargo fmt --check
• git diff --check
• Source and authored-line budget checks
• Cargo tests/build (deferred; no Cargo build/test command run)
• Manual runtime testing (not applicable to this mechanical extraction)

Closes #307