Add chain state indexing and RPC endpoint

[m-kus]

Add Chain State Management

This PR adds a chain state management system to track and maintain the Bitcoin chain state, which is essential for SPV verification. The implementation includes:

• New ChainState struct to store block height, total work, best block hash, current target, epoch start time, and previous timestamps
• ChainStateManager to handle state updates when new blocks are processed
• SQLite storage for chain states with serialization using bincode
• New RPC endpoint /chain-state/:block_height to retrieve chain state at a specific height
• Integration with the indexer to update chain state alongside MMR updates
• Refactored block header storage to separate it from MMR functionality

These changes enable proper tracking of chain parameters needed for SPV verification and provide a way for clients to access this information through the API.

[m-kus]

• Add chain state indexing and RPC endpoint #383 👈 (View in Graphite)
• Thread safe MMR #379
• Expose endpoint to fetch multiple block headers #377
• Single writer/multiple reader MMR store #376
• backend: remove file sink #375
• Fix typo #382 : 2 other dependent PRs (#378 , #381 )
• main

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