Track product page view for referral attribution.

Request body (JSON): - browserId (string, required): Client-generated browser fingerprint hash (djb2) - referrerId (string, optional): Referring user's visitorId from mm_rf URL param - currentUrl (string): Full URL of product page - host (string): Hostname - pathname (string): URL path - referrer (string): Document referrer or "$direct" - referringDomain (string): Referrer hostname or "$direct" - os (string): Operating system name - osVersion (string): OS version - browser (string): Browser name - device (string): Device identifier - deviceType (string): "Mobile", "Tablet", or "Desktop" - browserLanguage (string): Browser language (e.g., "en-GB") - screenHeight (int): Screen height in pixels - screenWidth (int): Screen width in pixels - viewportHeight (int): Viewport height in pixels - viewportWidth (int): Viewport width in pixels Response: { visitorId: string } - SHA256(browserId + clientIP)