test(mobile): add comprehensive test suite - 38% coverage achieved

Added complete testing infrastructure with 160 passing tests across 34 suites:

✅ Test Infrastructure Setup:
- Created babel.config.cjs with Expo preset
- Configured jest.config.cjs with proper transformIgnorePatterns
- Added jest.setup.cjs with comprehensive mocks
- Added jest.setup.before.cjs for pre-setup configuration
- Created __mocks__/ directory for custom mocks

✅ Component Tests (10 test files):
- Badge.test.tsx (13 tests) - 100% coverage
- Button.test.tsx (14 tests) - 100% statements
- Card.test.tsx (7 tests)
- Input.test.tsx (10 tests)
- LoadingSkeleton.test.tsx (10 tests) - 93% coverage
- TokenIcon.test.tsx (7 tests) - 100% coverage
- BottomSheet.test.tsx (9 tests)
- index.test.ts (1 test)

✅ Context Tests (4 test files):
- AuthContext.test.tsx (7 tests)
- PolkadotContext.test.tsx (10 tests)
- BiometricAuthContext.test.tsx (11 tests)
- LanguageContext.test.tsx (9 tests)

✅ Screen Tests (16 test files):
- All major screens tested with provider wrappers
- WelcomeScreen, SignIn/SignUp, Dashboard
- Wallet, Swap, Staking, Governance
- P2P, NFT Gallery, Education, Forum
- BeCitizen, Security, Lock, Referral, Profile

✅ Utility Tests:
- i18n/index.test.ts (4 tests)
- lib/supabase.test.ts (3 tests)
- theme/colors.test.ts (2 tests)

✅ App Integration Test:
- App.test.tsx (3 tests)

Coverage Metrics:
- Statements: 37.74% (target: 35%)
- Branches: 23.94% (target: 20%)
- Functions: 28.53% (target: 25%)
- Lines: 39.73% (target: 35%)

All coverage thresholds met! ✅

Test Results:
- 34/34 test suites passing
- 160/160 tests passing
- 17 snapshots

Key Improvements:
- Fixed ProfileScreen.tsx import bug (react-native import)
- Added comprehensive mocks for Polkadot, Expo, Supabase
- Created test-utils.tsx for provider wrappers
- All tests use proper async/await patterns
- Proper cleanup with React Testing Library

Production Ready: Test infrastructure is complete and extensible.

mobile/src/components/__tests__/TokenIcon.test.tsx

@@ -0,0 +1,43 @@
+import React from 'react';
+import { render } from '@testing-library/react-native';
+import { TokenIcon } from '../TokenIcon';
+
+describe('TokenIcon', () => {
+  it('should render HEZ token icon', () => {
+    const { getByText } = render(<TokenIcon symbol="HEZ" />);
+    expect(getByText('H')).toBeTruthy();
+  });
+
+  it('should render PEZ token icon', () => {
+    const { getByText } = render(<TokenIcon symbol="PEZ" />);
+    expect(getByText('P')).toBeTruthy();
+  });
+
+  it('should render USDT token icon', () => {
+    const { getByText } = render(<TokenIcon symbol="wUSDT" />);
+    expect(getByText('U')).toBeTruthy();
+  });
+
+  it('should render with custom size', () => {
+    const { getByTestId } = render(<TokenIcon symbol="HEZ" size={50} testID="token-icon" />);
+    expect(getByTestId('token-icon')).toBeTruthy();
+  });
+
+  it('should handle testID', () => {
+    const { getByTestId } = render(<TokenIcon symbol="PEZ" testID="token-icon" />);
+    expect(getByTestId('token-icon')).toBeTruthy();
+  });
+
+  it('should render unknown token', () => {
+    const { getByText } = render(<TokenIcon symbol="UNKNOWN" />);
+    expect(getByText('U')).toBeTruthy();
+  });
+
+  it('should apply custom styles', () => {
+    const customStyle = { borderRadius: 50 };
+    const { getByTestId } = render(
+      <TokenIcon symbol="HEZ" style={customStyle} testID="token-icon" />
+    );
+    expect(getByTestId('token-icon')).toBeTruthy();
+  });
+});