[SparkyFitness] Improve meal serving size logic for diary logging

## Is your feature request related to a problem? Please describe. When creating a meal, the current "Default Serving Size" field is unintuitive because it doesn't account for how many total servings a meal makes. As a result, when logging that meal in the diary, users are forced to enter decimal values (e.g., `.25` to represent 1 out of 4 servings) to get the correct nutrition. There is also no dedicated field to define how many total servings a meal yields, meaning users must manually track this information elsewhere, such as in the description field. Additionally, the "Total Nutrition" display reflects the full recipe rather than a per-serving breakdown, which is inconsistent with how nutrition labels work in practice. ## Describe the solution you'd prefer Split the current "Default Serving Size" field into two separate fields: 1. **Total Servings** — the number of servings the full meal yields (e.g., 4). The nutrition panel should use this value to calculate and display **per-serv