OFF data is sparse for fresh produce — spinach, oats, most frozen fruit
have no potassium. Added a curated fallback table (114 foods, USDA-sourced)
that injects estimated K/Ca/Mg at log time when OFF has no data.
How it works:
- data/fallback_nutrients.json: 114 foods with mg/100g values
- FallbackTable: case-insensitive exact + substring name matching
- log_food: injects _est keys (potassium_100g_est etc.) when OFF missing
- sum_nutriments: tries OFF value first (grams×1000), then _est (already mg)
Results for today's smoothie + lunch:
- Potassium: 691mg → 2,530mg (47% of 5400mg goal)
- Calcium: 14mg → 304mg (30% of 1000mg goal)
- Magnesium: 61mg → 330mg (73% of 450mg goal)
38 tests passing (7 new: fallback lookup, est fallback, OFF vs est priority)
