Function parse_fidel_webhook 

pub fn parse_fidel_webhook(
    body: &[u8],
    privacy: &PrivacyLayer,
) -> Result<NormalizedTransaction, WebhookError>

Parse Fidel webhook and normalize

Privacy Protocol

This function implements Double-Blind Vaulting:

1. Parse the raw payload
2. IMMEDIATELY hash card_id to fingerprint
3. Drop the raw card_id (it’s moved into the hasher)
4. Return only normalized data with fingerprint