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

## Goal

Enable [Kupo](https://github.com/IntersectMBO/kupo) to use cardano-rpc as a drop-in replacement for its [Ogmios](https://github.com/IntersectMBO/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`** - #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`** - #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`** - #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` (#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.