Fix CLEANED app and batch output compatibility

[M-Emmanuel]

Ensure combineOutputs returns app-compatible plot outputs while preserving batch outputs.

• Return on_farm_table, land_required, nitrogen_balance, and water_use_per_feed_item as explicit top-level app outputs.
• Normalize GHG, land, N balance, and water plotting columns to numeric data frames.
• Keep detailed batch outputs such as nitrogen_balance_detail and land_required_summary.
• Update differences parsing to use batch-detail tables and row-style livestock productivity outputs.
• Avoid duplicate output names when combining app and batch result objects.