Clarify startup setup and add setup check

[wanqinghd]

Summary

• document the install, environment, and startup flow more clearly
• add python main.py --check so users can see missing dependencies/config before starting the microphone loop
• make .env, microphone config, and Vosk imports more robust across local setups
• add the missing requests dependency

Verification

• python3 -m py_compile main.py helpers/*.py
• python3 main.py --check
• python3 main.py --help

Fixes #7
/claim #7

AI-assisted contribution prepared with Codex. I reviewed the repository context and ran the verification commands above.

[opirebot]

👀 We've notified the reward creators here.
Make sure your payment account is ready to receive the payment for your hard work 💪