Fix issue #1870: Add height range filtering to /boxes/unspent endpoint

[dimension-drifter]

Problem:
The /wallet/boxes/unspent endpoint currently fetches ALL unspent wallet boxes from the database and then filters them in memory by height parameters (minInclusionHeight and maxInclusionHeight). This is inefficient, especially for wallets with many boxes.
The /wallet/transactions endpoint already implements efficient height-based filtering by querying the database directly with a height range using walletTxsBetween().

Solution:
This PR implements the same pattern for /wallet/boxes/unspent:

1. Added walletUnspentBoxesByInclusionHeight() method to WalletRegistry to query boxes by height range directly from DB
2. Updated GetWalletBoxes message to include minHeight and maxHeight parameters
3. Updated ErgoWalletService.getWalletBoxes() to use height-based DB queries when height parameters are specified
4. Updated the entire call chain (ErgoWalletActor, ErgoWalletReader, WalletApiRoute) to pass height parameters through