[WIP] Fix issues in email_classifier.py without altering logic

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Fix the following issues in email_classifier.py without introducing new features or changing the overall logic:

1. Remove the duplicate import of google.generativeai.

2. Fix the label color mapping mismatch: Ensure the keys in color_map match the keys in config.EMAIL_LABELS (change 'Important' to 'IMPORTANT' and 'Spam' to 'SPAM' in color_map).

3. Improve HTML body extraction: Strip HTML tags from text/html bodies using a simple regex or library to get plain text for body_preview.

4. Enhance response parsing in classify: Make the regex more robust to handle various Gemini response formats, and add better validation for the extracted label.

5. Add more comprehensive error handling for Gmail API calls, including retries for network issues and quota errors.

6. Add configuration validation in main() for other config values like LOG_LEVEL, MAX_EMAILS_PER_RUN, etc., to prevent runtime errors.

7. In _refresh_credentials, add fallback to interactive auth if refresh fails in cloud environments (though interactive might not be possible, log clearly).

Ensure all changes are minimal and maintain backward compatibility. Do not add tests in this PR; focus only on bug fixes.

This pull request was created from Copilot chat.

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[Rajrooter]

@copilot No problem you write code I will copy paste REMEMBER:-without changing anything.