[Refactor]: Move Launcher Connection Handling to Backend

[daGscheid]

Refactor Description

Currently, the Stereum launcher handles the connection logic (e.g., checking connection state, managing retries, displaying errors) on the frontend.

• Identify all connection-related logic currently in the frontend (Launcher).
• Implement equivalent functionality in the backend service.
• Expose necessary APIs for the frontend to query connection status.
• Ensure all edge cases (e.g., node unreachable, timeouts, network changes) are gracefully handled on the backend.
• Update frontend to consume the new connection status API and remove redundant logic.
• Add tests for backend connection handling.

Reason for Refactor

To streamline architecture, improve maintainability, and enable better error handling, this logic should be migrated to the backend.

Potential Risks

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