restore error-message dialog

[isamu]

The error-meesage div was removed in the bc3866ffec5c5f7dc186c55f718816ab036de2d7 commit. Since the error could no longer be displayed, I restored it.

Summary by CodeRabbit

• New Feature: Added an error message display to the main page. This feature will enhance user experience by providing clear and immediate feedback when an error occurs. The error message, initially hidden, will appear when needed and can be easily dismissed by the user with a close button. This change improves the software's intuitiveness and user-friendliness.

[coderabbitai[bot]]

Walkthrough

The change introduces an error message section to the main HTML page. This section is initially hidden and can be used to display error messages to the user with a close button.

Changes

File	Summary
templates/index.html	Added an error message section to the HTML page. The section is initially hidden and includes a close button.

🐇

In the land of code, where the shadows lie, An error message, hidden from the eye. With a button to close, and a message to show, A change has been made, to let the user know. 🎉

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