feat: implement 1inch balance plugin

[devin-ai-integration]

Implements 1inch balance plugin with getAggregatedBalancesAndAllowances tool.

Changes:

• Add Balance service with getAggregatedBalancesAndAllowances tool
• Use fetch for API calls
• Add proper type definitions and parameter validation
• Implement error handling
• Follow code style guidelines

Link to Devin run: https://app.devin.ai/sessions/1c1499ca600c4f42b2f3128c6d24fb27

[devin-ai-integration]

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Latest commit: 9be14fc

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