feat: Implement blockchain indexer API routes

[lilycom02]

This PR implements the blockchain indexer API routes with the following features:

• Add block information query endpoint
• Add transaction information query endpoint
• Add address transaction history endpoint with pagination
• Add latest blocks and transactions list endpoints
• Add universal search endpoint
• Implement unified response format and error handling
  The implementation provides a complete set of REST APIs for blockchain data querying, which will serve as the backend foundation for the blockchain explorer frontend.

[jasonandjay]

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