🧹 [code health] Remove legacy fallback logic from Applications extension

[Dor-bl]

🎯 What: Removed the deprecated try/except fallback logic in all app management methods (activate_app, background_app, is_app_installed, install_app, remove_app, terminate_app, query_app_state, app_strings) within appium/webdriver/extensions/applications.py. The class now relies exclusively on mobile: scripts.

💡 Why: This improves maintainability by removing legacy endpoints (e.g. Command.ACTIVATE_APP, Command.BACKGROUND), simplifying the control flow, and eliminating the need for CanRememberExtensionPresence checking logic, aligning the codebase with standard Appium 2 behavior.

✅ Verification: Verified by compiling the file, running ruff for linting, and executing the app_test.py unit tests with pytest, which all passed successfully.

✨ Result: A cleaner, simpler Applications extension class with legacy cruft removed and no impact to intended public API usage.

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PR created automatically by Jules for task 9502228454495900322 started by @Dor-bl

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