feat(compat): add Cipherscan API adapter

[gustavovalverde]

Summary

Adds zinder-compat-cipherscan, an adapter that serves Cipherscan's current HTTP and WebSocket contracts from Zinder. Cipherscan can use Zinder as its chain-data backend without changing its routes, query behavior, or response formats.

Surface added

• Chain status, block search and detail, transaction search and detail, raw transactions, transaction broadcast, and commitment-root lookup.
• Mempool summaries and transaction lookup, plus reconnectable block and mempool WebSocket events.
• Transparent address activity, rich-list data, supply summaries, value-pool balances, flows, and history.
• Network statistics, fee analytics, mining metrics, mining rewards, and mining pool distribution.
• Shielded transaction history, protocol statistics, anonymity-set and shielding-distribution analytics, Blend Check, common amounts, and transaction linkability.
• Reorg history, displaced block details, fork comparisons, and Sapling, Orchard, and Ironwood commitment roots.
• Current and bounded historical market-price endpoints.

Mining distribution

Adds a product-neutral, time-indexed block-production projection with durable coverage, restart recovery, atomic reorg rollback, and continuation cursors that remain stable during ordinary chain advancement. The adapter uses that contract to preserve Cipherscan's supported periods, fallback coercion, exact paid-fee totals, five-minute raw-period cache keys, response shape, and adapter-owned pool registry.

Architecture boundary

Zinder owns canonical chain facts, reusable projections, coverage and freshness metadata, and product-neutral gRPC queries. The adapter owns Cipherscan route names, request coercion, response envelopes, display units, cache behavior, pool metadata, and product formulas.

Labels, node and GeoIP inventory, mining behavior products, turnstile classification, cross-chain analytics, name services, identity-risk analytics, finalizer registries, public fork reports, physical chain-size history, and server-side viewing-key scanning remain explicitly sidecar-owned or unavailable. This change does not add Zinder schemas for those surfaces.

The endpoint ownership matrix is documented in docs/plans/cipherscan-adapter-architecture.md. The block-production projection is specified in docs/adrs/0033-time-indexed-block-production.md. Setup, Cipherscan wiring, deployment topology, configuration, and operational probes are documented in services/zinder-compat-cipherscan/README.md.