[_]: feat/local storage, config and sdk services

[xabg2]

New services have been added:

• Config service: manages environment variables in a centralized way.
• Local storage service: provides a layer over the native localStorage API, so we can save or retrieve the user, token, or mnemonic with simple function calls instead of manipulating localStorage manually.
• SDK service: manages SDK instances for auth, user, and payments, providing a single point of access.
• Payment service: handles payment-related logic, such as retrieving the user’s tier and subscription details.

Besides:

• Basic Vitest setup has been added, along with tests covering the services mentioned above.
• Basic CI workflow added to automatically run tests and build when a PR is opened targeting master.

[larryrider]

maybe it makes more sense to run the build before the tests 🤔

[xabg2]

Mmmm, yeah, could be.