[WIP] Add GPLv3 license to README and license file

[Copilot]

Plan to Add GPLv3 License

• Create LICENSE file with full GPLv3 license text
• Update README.md to add license badge and license section
• Update loading screen footer in index.html to mention GPLv3 license
• Verify all changes are correct

Original prompt

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This section details on the original issue you should resolve

<issue_title>add GPLv3 license</issue_title>
<issue_description></issue_description>

<agent_instructions>add the gpl license to the readme and the license file. maybe in the loading page if you seem fit.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes add GPLv3 license #14

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