feat(mobile): add Sign Up screen and reusable useApi hook; implement …

[Cedarich]

Summary

• Implemented a Sign Up screen that validates input, calls the signup API, shows loading and error states, and navigates to login on success.
• Added a reusable, type-safe useApi hook for handling request state and errors.
• Added authApi.signUp that posts to /auth/signup via the shared apiClient.

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Changes

• mobile/app/signup.tsx

  • Created SignUpScreen using Formik + Yup
  • Added ActivityIndicator for loading, error display, and success Alert
  • Implemented navigation with expo-router

• mobile/services/authApi.ts

  • Added authApi.signUp(payload) returning AxiosResponse<{ message: string }>

• mobile/services/useAPI.ts

  • Added generic useApi<T, P> hook to manage data, loading, and error using AxiosResponse typing

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How it Works

• Validation:

  • Yup ensures name, email, password, and confirm password are correct.

• On Submit:

  • useApi calls authApi.signUp and returns { success, data, error }.
  • On success, shows an Alert with the server message and navigates to /login.
  • On error, displays the API error message or a generic fallback.

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Test Plan

1. Start the mobile app and navigate to the Sign Up screen.
2. Enter invalid inputs → verify inline validation errors.
3. Enter valid inputs → submit and confirm:
   • Loading spinner appears.
   • Request completes and success Alert is shown.
4. Simulate a server/network error → verify error message under the form.
5. Confirm app navigates to /login after a successful signup.

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Notes / Dependencies

• Ensure apiClient is configured with the correct base URL.
• Backend must expose POST /auth/signup.
• Project must include Axios and React types for TypeScript.
• No breaking changes to existing screens.

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