Report Generation: Switching from OpenAI SDK to Google ADK and removing OpenAI dependencies

[lotif]

Summary

Switching from OpenAI SDK to Google ADK on Report Generation agent to match the other agents. Removing OpenAI dependencies.

Some extra code was needed to parse the response of the agents which is a bit trickier with Google ADK.

Clickup Ticket(s): NA

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📝 Documentation update
• 🔧 Refactoring (no functional changes)
• ⚡ Performance improvement
• 🧪 Test improvements
• 🔒 Security fix

Changes Made

• Switching from OpenAI SDK to Google ADK on report generation agents
• Modifying the demo and evaluate code accordingly
• Added an event parser to parse the response of the google models
• Removing OpenAI dependencies from pyproject.toml
• Updating .env.example and the Config class to remove OpenAI env vars

Testing

• Tests pass locally (uv run pytest tests/)
• Type checking passes (uv run mypy <src_dir>)
• Linting passes (uv run ruff check src_dir/)
• Manual testing performed (describe below)

Manual testing details:
Ran the demo UI and the evaluation script

Checklist

• Code follows the project's style guidelines
• Self-review of code completed
• Documentation updated (if applicable)
• No sensitive information (API keys, credentials) exposed