Integrate UI tests tool (JUnit or Robolectric)

[tomastiminskas]

Context

UI Test coverage needs to be added to the app

The goal is to test some basic UI interactions in the main views and their expected results.

1. Add any needed configuration for the selected test tool (JUnit, Robolectric, UI Automator, etc).
2. Solve the issue we faced before described in this comment: [Tests] Create UI tests on the Chat view using JUnit or Robolectric #703 (comment)

Acceptance Criteria

• Integrate UI test coverage tool and run a small UI test

[caydyan]

Submitted draft PR for this bounty: #744

It adds Hilt instrumentation test tooling plus a minimal Espresso launch smoke test for MainActivity.

Bounty address: bc1qev5ant33v5y89qqjvcf4mh9hlax5svqf5xd7gc

[caydyan]

Status update for PR #744: it is now open, non-draft, and mergeable at head 60c562d. The PR body includes the validation command and BTC payout address, and I can make focused revisions if review asks for any.