this pull request introduces a comprehensive test suite for the torrra application using pytest. it adds unit, integration, and snapshot tests to ensure code quality, prevent regressions, and validate core functionality.

KEY ADDITIONS:

• CORE LOGIC TESTS: unit tests for core components like Config and Cache have been added, ensuring they behave as expected in isolation.
• CLI TESTS: the click CLI is now tested using CliRunner, with application-launching functions mocked to verify argument parsing and command dispatch.
• SCREEN & UI TESTS: the textual UI screens (WelcomeScreen and SearchScreen) are tested using pytest-textual's pilot to simulate user interaction and assert UI state changes.
• SNAPSHOT TESTING: pytest-textual-snapshot has been configured to capture SVG snapshots of UI screens, protecting against unintended visual regressions.