chore: update package.json for testing scripts and dependencies

- Added unit and end-to-end testing scripts to package.json.
- Included detox for end-to-end testing and jest-circus for improved test execution.

feat: add testID to LandingScreen logo for better testing

- Added testID attribute to the logo image in LandingScreen for easier identification in tests.

feat: create tokens.ts to re-export design tokens

- Introduced tokens.ts to re-export shared design tokens from lightTheme for consistent imports.

app/src/screens/LandingScreen.tsx

@@ -35,6 +35,7 @@ export default function LandingScreen() {
         style={styles.logo}
         resizeMode="contain"
         accessibilityLabel="My Mobile Agent"
+        testID="landing-logo"
       />
     </View>
   );

app/src/theme/tokens.ts

@@ -0,0 +1,3 @@
+// Re-export shared design tokens from lightTheme so both
+// "theme/tokens" and "theme/lightTheme" imports resolve correctly.
+export { colors, spacing, typography, borderRadius } from './lightTheme';