feat: add tool to check alternate_subcategory consistency with category

[Copilot]

Adds tools/check-alternate-subcategory-consistency.js, a command-line tool that iterates all tossups and bonuses in the database and logs any question whose alternate_subcategory is inconsistent with its category.

Logic (using CATEGORY_TO_ALTERNATE_SUBCATEGORIES from quizbowl/categories.js):

• If the category has a non-empty alternate subcategory list: the question's alternate_subcategory must be one of those values — null/undefined is flagged as inconsistent.
• If the category has an empty alternate subcategory list: the question's alternate_subcategory must be null/undefined — any set value is flagged.

Usage:

node tools/check-alternate-subcategory-consistency.js