feat(auth): add user identity verification system with new screens

Add comprehensive identity verification flow including:
- New verification guide screen at /verification-guide for selecting identity type
- New verification form screen at /verification-form for submitting verification documents
- Verification settings screen at /profile/verification for managing verification status
- Move terms and privacy policy to root-level routes (/terms, /privacy)
- Update login to require active terms agreement checkbox
- Database: add in-memory fallback when OPFS is unavailable on web

BREAKING CHANGE: Terms and privacy policy routes moved from /profile/terms and /profile/privacy to /terms and /privacy

app/(app)/(tabs)/profile/_layout.tsx

@@ -40,6 +40,7 @@ export default function ProfileStackLayout() {
       <Stack.Screen name="about" options={{ title: '关于我们' }} />
       <Stack.Screen name="terms" options={{ title: '用户协议' }} />
       <Stack.Screen name="privacy" options={{ title: '隐私政策' }} />
+      <Stack.Screen name="verification" options={{ title: '身份认证' }} />
     </Stack>
   );
 }

app/(app)/(tabs)/profile/verification.tsx

@@ -0,0 +1,5 @@
+import { VerificationSettingsScreen } from '@/screens/profile/VerificationSettingsScreen';
+
+export default function VerificationSettingsPage() {
+  return <VerificationSettingsScreen />;
+}