feat: add event listeners for `bridgeTokensBack()` and `bridgeNonFungibleTokensBack()`

[thomas779]

Problem
The frontend lacks the necessary event listeners to handle bridgeTokensBack() and bridgeNonFungibleTokensBack() events emitted by the smart contract. This omission hinders the real-time update of UI components and user feedback.

Solution
Implement event listeners in the frontend to capture and handle events emitted by the smart contract for bridgeTokensBack() and bridgeNonFungibleTokensBack().

Requirements

• Create and set up listeners for both bridgeTokensBack() and bridgeNonFungibleTokensBack() events.
• Ensure that the UI is updated in real-time when these events are emitted.
• Implement any additional logic required to handle these events gracefully.

Additional Information
This step is crucial for providing a smooth and responsive user experience. It ensures that users receive immediate feedback on their actions related to bridging tokens.