Cleanup: remove unused variables in lb_app ui_interfaces

## Problem
`lb_app/ui_interfaces.py` contains unused variables in adapter methods.

## Evidence
- `arch_report/by_target/lb_app/vulture.txt:1`

## Plan
1. Remove unused variables or mark with underscore where required by interface.
2. Ensure mypy/ruff remains clean.

## Validation
- `uv run pytest tests/unit/lb_app/test_*ui*.py`
- `./scripts/arch_audit.sh lb_app`
