fix(common): make ResultType.mapError invoke its callback

[amaury901130]

Description

ResultType.mapError (modules/common/lib/core/result_type.dart) returned TError(e.error) without calling the callback. AuthCubit.login and signUp handle results like this:

authResult
  ..mapSuccess((_) => isLogin())
  ..mapError((failure) => isError(failure));

So on a TError, nothing was emitted and the cubit stayed in RLoading forever: the button kept spinning and no error was shown. The bug is hidden today only because the example AuthRepositoryImpl always succeeds. It surfaces as soon as a real backend returns an error.

Fix: mapError now calls the callback. If the callback returns an Exception, that replaces the error (transform semantics); anything else keeps the original error (side-effect semantics, as AuthCubit uses it). TSuccess is unaffected.

Also:

• Adds modules/common/test/core/result_type_test.dart, the first tests in common, covering mapError and mapSuccess.
• Adds modules/common/test to sonar.tests.

Issue

known-issues #1 in #117.

Preview

N/A

Notes:

• ⚠️ Not compiled or run locally, because no Flutter SDK was available where this was written. Please run cd modules/common && flutter pub get && flutter test and melos analyze before merging.
• Doesn't conflict with chore: adopt FVM, migrate to Melos 7, upgrade dependencies #116. That PR doesn't touch result_type.dart or sonar-project.properties.
• After merge, drop entry Create Base GitHub Project #1 from docs/architecture/known-issues.md, and the mapError warnings in CLAUDE.md rule 3 and feature-guide.md (docs: add CLAUDE.md and architecture/development docs #117).

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