Create Controller Contract to Orchestrate the System

[brolag]

Description: Implement the controller contract to orchestrate the minting and burning of eUSD tokens based on the users' ETH collateral in the vault.

Subtasks:

• Implement logic to check user collateral in the vault before minting eUSD.
• Implement the mintEUSD() function to mint eUSD based on collateralization ratio.
• Implement the burnEUSD() function to burn eUSD and optionally release collateral.
• Set up interactions between the controller, vault, and eUSD token contracts.
• Write unit tests to ensure proper minting, burning, and collateral management.

Acceptance Criteria:

• mintEUSD() only mints eUSD if the user has sufficient collateral.
• burnEUSD() correctly burns tokens and unlocks collateral (if applicable).
• Unit tests for minting, burning, and collateral checking pass.