restored 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 user interface. This will enhance user experience by providing clear and immediate feedback when an error occurs. The error message is initially hidden and will only appear when needed.
• Chore: Adjusted the application's operating port from 8080 to 8081. This change is part of our ongoing system optimization and will not affect the user experience directly.

[coderabbitai[bot]]

Walkthrough

The changes primarily involve a shift in the server port from 8080 to 8081 in main.py and the addition of an error message section in the index.html file. This error message is initially hidden and can be displayed when needed.

Changes

File	Summary
main.py	The server port has been changed from 8080 to 8081.
templates/index.html	An error message section has been added. This section is initially hidden and includes a close button.

🐇💻

In the land of code, changes are afoot,

A new port is open, giving the old one the boot.

An error message hides, ready to show,

When things go awry, it's in the know.

So here's to the changes, may they serve you well,

In the grand scheme of code, only time will tell. 🎉🥕

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