Revert "feat: WhatsApp notification helper + phase 4 migration (recheck_round, WhatsApp settings)"

This reverts commit b6845f5bb5.

lib/notifications/whatsapp.ts

@@ -1,42 +0,0 @@
-export async function sendWhatsAppMessage(
-  phoneNumber: string,
-  templateName: string,
-  parameters: string[],
-  phoneNumberId: string,
-  accessToken: string,
-): Promise<void> {
-  const sanitized = phoneNumber.replace(/[^0-9]/g, '')
-  if (!sanitized) return
-
-  const body = {
-    messaging_product: 'whatsapp',
-    to: sanitized,
-    type: 'template',
-    template: {
-      name: templateName,
-      language: { code: 'en_US' },
-      components: [
-        {
-          type: 'body',
-          parameters: parameters.map(text => ({ type: 'text', text })),
-        },
-      ],
-    },
-  }
-
-  const res = await fetch(
-    `https://graph.facebook.com/v19.0/${phoneNumberId}/messages`,
-    {
-      method: 'POST',
-      headers: {
-        'Content-Type': 'application/json',
-        'Authorization': `Bearer ${accessToken}`,
-      },
-      body: JSON.stringify(body),
-    }
-  )
-
-  if (!res.ok) {
-    throw new Error(`WhatsApp API error: ${res.status}`)
-  }
-}