Add validators, widget updates, tests, fixtures, test doubles and CI workflow

[Faifor]

Motivation

• Implement comprehensive unit/widget/integration coverage for auth refresh logic, error mapping, input validators, and key UI flows as requested (login, cart, admin reports).
• Provide deterministic test data and doubles so tests are repeatable and do not depend on external services.
• Surface validation and submit/loading states in screens to improve UX and make core flows testable.
• Add CI automation to run the suite on push/PR using the standard flutter test command.

Description

• Added centralized validators in lib/core/validation/input_validators.dart for profile name, quantity, promo codes, and filters (date range and min-total checks).
• Converted a few presentation screens to stateful components and added small behaviors: AuthScreen supports onSubmit and submit state, CartScreen supports qty changes and total calculation, and AdminScreen supports report filters with onApplyFilters.
• Added a broad set of tests under test/ including unit tests for validators, RefreshSessionUseCase, refresh-token interceptor behavior, and error mapper, widget tests for login/cart/admin UIs, and integration-style widget tests for auth flow, cart+checkout, and admin reports.
• Introduced test doubles and JSON fixtures in test/doubles/mock_repositories.dart and test/fixtures/*.json, and added a GitHub Actions workflow .github/workflows/ci.yml plus a Testing section in README.md documenting flutter test --reporter expanded.

Testing

• Added unit tests (test/core/*, test/features/*), widget tests (test/widget/*), and integration-style widget tests (test/integration/*) but these are created and committed rather than executed here.
• Attempted to run flutter test locally in this environment, but it could not be executed because the Flutter SDK is not available (flutter: command not found).
• CI is configured to run flutter pub get and flutter test --reporter expanded in GitHub Actions via .github/workflows/ci.yml so tests will run on push/PR in the repository environment.

---

Codex Task

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 4409aa6b9e

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Reset submit state when login request fails

If onSubmit throws (for example, on a network/auth failure), the await exits _submit before _isSubmitting is set back to false, leaving the button disabled with a spinner and no way to retry in the same screen state. This makes transient backend errors effectively block the login UI until a rebuild, so the call should be wrapped in try/finally (and optionally surfaced as an error message).

Useful? React with 👍 / 👎.

[chatgpt-codex-connector]

Clear admin loading state when filter fetch throws

A thrown exception from onApplyFilters skips the _isLoading = false update, so the Apply button stays disabled and the loading indicator persists indefinitely after a failing fetch. In production this can happen on API errors/timeouts and prevents users from retrying filters without leaving the page; use try/finally to always restore loading state.

Useful? React with 👍 / 👎.