[FEAT] Write data_network module in mobile app

[PavMash]

Feature description

Make research and implement data_network module. It includes HTTP client connected to backend and repositories that provide API for other app components.

What is needed to be done

• Make research: which library to use, how to use it
• Write HTTP client
• Implement endpoint functions and repositories for all network-related functionality

Acceptance Criteria

• Library is chosen, choice is explainable
• Client successfully connects to server
• All required functionality is implemented
• APIs are clear and useful