[END 3565] fix: catch and display failed to broadcast error

[teebszet]

🔘 PR Type

• Bugfix

📜 Background

Provide a brief explanation of why this pull request is needed. Include the problem you are solving or the functionality you are adding. Reference any related issues.

Issue Link: #[issue_number]
Context Link (if applicable):

🔄 Changes

• add an error message for when stacks speed up fails to sign and broadcast
• updated the error message to remove the 'microblock' part
• fix styling of error toasts

🖼 Screenshot / 📹 Video

✅ Review checklist

Please ensure the following are true before merging:

• Code Style is consistent with the project guidelines.
• Code is readable and well-commented.
• No unnecessary or debugging code has been added.
• Security considerations have been taken into account.
• The change has been manually tested and works as expected.
• Breaking changes and their impacts have been considered and documented.
• Code does not introduce new technical debt or issues.

[DuskaT021]

Lgtm