feat: Initialize project structure

[google-labs-jules]

Sets up a standard Python project structure with:

• src/proactivemind_ai for source code
• tests/ for tests
• requirements.txt for dependencies
• .gitignore for ignoring files
• An updated README.md

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PR created automatically by Jules for task 14300765316099737195 started by @AUTOGIO

[google-labs-jules]

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