Verifies whether the provided mobile numbers are registered and active in the system.
This endpoint requires Bearer (JWT) authentication obtained from /auth/authenticate.

Behavior:

• Normalizes input mobile numbers to digits-only form (removes leading +, 00 or local 0).
• Performs a single batch check and returns two lists: foundNumbers and notFoundNumbers.

Limits & validation:

• Maximum 100 mobile numbers per request.
• mobileNumbers cannot be null or empty.
• Mobile number format validated by the API validator; validation failures return VALIDATION_ERROR.

Common error codes: INVALID_PAYLOAD, EMPTY_MOBILE_NUMBERS, MAX_ITEMS_EXCEEDED, VALIDATION_ERROR, MOBILE_NUMBERS_NOT_FOUND, DB_VERIFICATION_ERROR.