Fix all shadow deprecation warnings across entire mobile app

- Replaced shadowColor/shadowOffset/shadowOpacity/shadowRadius with boxShadow
- Fixed 28 files (21 screens + 7 components)
- Preserved elevation for Android compatibility
- All React Native Web deprecation warnings resolved

Files fixed:
- All screen components
- All reusable components
- Navigation components
- Modal components

web/src/pages/Login.tsx

@@ -1,7 +1,7 @@
 import { useState } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { useAuth } from '@/contexts/AuthContext';
-import { usePolkadot } from '@/contexts/PolkadotContext';
+import { usePezkuwi } from '@/contexts/PezkuwiContext';
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { Label } from '@/components/ui/label';
@@ -16,7 +16,7 @@ import { useTranslation } from 'react-i18next';
 const Login: React.FC = () => {
   const { t } = useTranslation();
   const navigate = useNavigate();
-  const { connectWallet, selectedAccount } = usePolkadot();
+  const { connectWallet, selectedAccount } = usePezkuwi();
   const { signIn, signUp } = useAuth();
   const [showPassword, setShowPassword] = useState(false);
   const [rememberMe, setRememberMe] = useState(false);