Merging from main

[Basigli]

This pull request makes minor improvements to the codebase by updating variable declarations from let to const in several places, enhancing code clarity and immutability. No functional changes are introduced.

Backend and frontend code quality improvements:

• Changed variable declarations from let to const in the polishNutrients method in both backend/src/utils/FoodItemConverter.ts and frontend/src/utils/FoodItemConverter.ts to indicate that the filtered nutrient arrays are not reassigned. [1] [2]
• Updated user ID variable declarations from let to const in backend/test/routes/recipesRoutes.test.ts for consistency and to prevent reassignment.
• Changed macroToUpdate declaration from let to const in frontend/src/store/intakeStore.ts for improved code safety.