Captures base per-unit values (calories/protein/carbs/fat/sugar/fiber
divided by original quantity) when draft first appears. When quantity
changes, recalculateMacros() multiplies base values by new quantity.
Example: AI drafts "1 medium banana" at 105 cal. User changes
quantity to 2.0 → calories becomes 210, protein doubles, etc.
Values round to integers for calories, 1 decimal for macros.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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