fix: remove hardcoded WhatsApp fallback and use environment variables

.env.example

@@ -40,7 +40,7 @@ R2_PUBLIC_URL=              # Public URL of the bucket (e.g. https://pub-xxx.r2.
 
 # ─── Frontend ──────────────────────────────────────────────────────────────────
 VITE_CLIENT_URL=https://your-frontend.netlify.app
-VITE_WHATSAPP_NUMBER=221786016142  # Without + prefix, for wa.me links
+VITE_WHATSAPP_NUMBER=221XXXXXXXXX  # Replace with your production WhatsApp Bot number
 
 # ─── Internal (Worker → API) ───────────────────────────────────────────────────
 API_URL=http://localhost:3001   # In prod: full URL of the Fastify API

apps/web/src/App.tsx

@@ -3,7 +3,8 @@ import { useEffect, useState } from 'react';
 import { BookOpen, FileText, Smartphone, ArrowRight, Phone, CheckCircle, Download, AlertCircle } from 'lucide-react';
 import PrivacyPolicy from './PrivacyPolicy';
 
-const WA_NUMBER = import.meta.env.VITE_WHATSAPP_NUMBER || '221786016142';
+const WA_NUMBER = import.meta.env.VITE_WHATSAPP_NUMBER || 'VITE_WHATSAPP_NUMBER_MISSING';
+// NOTE: VITE_WHATSAPP_NUMBER must be set in the production environment (e.g. Railway/Netlify)
 const API_URL = import.meta.env.VITE_API_URL || 'http://localhost:3001';
 
 function Navbar() {