gRPC: Replace Ogmios as Kupo's chain data source with cardano-rpc gRPC

[carbolymer]

Goal

Enable Kupo to use cardano-rpc as a drop-in replacement for its Ogmios backend.
Kupo currently uses Ogmios for chain synchronisation via WebSocket/JSON-RPC.
The same capability can be provided natively by cardano-rpc over gRPC, eliminating the need for a separate Ogmios process.

Kupo's Ogmios usage

Kupo depends on exactly three Ogmios methods:

Ogmios method	Mini-protocol	Purpose
findIntersection	ChainSync	Resume sync from a known chain point
nextBlock	ChainSync	Stream blocks (RollForward/RollBackward) with full block data
queryNetwork/genesisConfiguration	Network query	One-shot Byron genesis bootstrap (optional if local genesis files available)

Additionally, Kupo's HTTP API uses a separate Ogmios connection for ad-hoc historical block lookups (e.g. the /metadata endpoint fetches a block by slot on demand).

Required gRPC services

1. SyncService.FollowTip - gRPC: Implement FollowTip (UTxO RPC SyncService) in cardano-rpc #1219
   Server-streaming RPC delivering blocks as applied/rolled back.
   Must carry full block data (transactions, inputs, outputs, datums, scripts, redeemers, metadata).
   This is the primary blocker - replaces Ogmios's findIntersection + nextBlock streaming.

2. SyncService.FetchBlock - gRPC: Implement FetchBlock (UTxO RPC SyncService) in cardano-rpc #1216
   Retrieve a full block by chain point.
   Required for Kupo's HTTP API endpoints that perform ad-hoc historical block lookups (e.g. /metadata).

3. QueryService.ReadGenesis - gRPC: Implement ReadGenesis (UTxO RPC QueryService) in cardano-rpc #1217
   Return genesis configuration for all eras.
   Only required when Kupo cannot read genesis files from disk.

Prerequisites

• ADR-019 (node kernel access) - direct ChainDB access is needed for efficient block streaming and block-by-point retrieval.
  Current N2C IPC (one connection per request, double serialisation) cannot support this.

Not required for this goal

• ReadTip (gRPC: Implement ReadTip (UTxO RPC SyncService) in cardano-rpc #1218) - same SyncService cluster, likely lands alongside FollowTip, but Kupo does not use it (tip comes back in FollowTip responses)
• SubmitTx, EvalTx - already implemented, Kupo does not use them
• Mempool watching, stake/governance queries - Kupo does not use them

Downstream integration

Once the gRPC services exist, Kupo needs a new ChainProducer backend (alongside its existing CardanoNode, Ogmios, Hydra backends) that connects via gRPC instead of WebSocket.