🐛 fix(inspect): Use null pool for async engine

[MarkRedeman]

📝 Description

This fixes an issue where the training worker wasn't able to get a lock on the sqlite database. As a result when it tried to get all pending jobs the query it would execute would stall indefinitely.

✨ Changes

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• 🚀 New feature (non-breaking change which adds functionality)
• 🐞 Bug fix (non-breaking change which fixes an issue)
• 🔄 Refactor (non-breaking change which refactors the code base)
• ⚡ Performance improvements
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• 🧪 Tests (adding/modifying tests)
• 📚 Documentation update
• 📦 Build system changes
• 🚧 CI/CD configuration
• 🔧 Chore (general maintenance)
• 🔒 Security update
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)

✅ Checklist

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• 🧪 I have written tests that support my changes and prove that my fix is effective or my feature works (if applicable).
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