Clarify startup setup and microphone config

[Obvidio]

/claim #7

Summary

• Add a step-by-step getting started guide for a fresh BonziAssist setup.
• Load environment variables from the project root .env while keeping helpers.env compatibility.
• Save and read microphone configuration from the existing root mic_config.json file instead of a missing config directory.
• Link the new guide from the README.

Verification

• Ran: python -m py_compile main.py helpers/llm.py helpers/mic.py helpers/tts.py

This should help new users understand exactly how to start the app and avoid the current first-run path issues around .env and microphone config.

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[Obvidio]

Opire claim metadata:

Fixes #7
Issue: #7
PR: #29

Verification repeated locally:
python -m py_compile main.py helpers/llm.py helpers/mic.py helpers/tts.py

[Obvidio]

Payment account is now connected in Opire. This PR remains ready for review; local verification still passes:

python -m py_compile main.py helpers/llm.py helpers/mic.py helpers/tts.py

Please let me know if any maintainer changes are needed.