feat(zcash): add bridge UI, Service2 and wallet companions

[a-shannon]

Add the transparent Zcash UI and Service2 path

Summary

Add Zcash network and catalogue data, Service2 reserve-balance ingestion, address
validation, lock construction, receipt verification, and bounded Zallet/Ergo
companions. Zallet accepts Mainnet configurations, while the separate Ergo
companion is devnet-only. Execution evidence is local and does not qualify a
Mainnet wallet or operator path.

Validation

• A clean Node 22.18.0/npm 11.6.2 install built 36 dependency packages and resolved
  only abstract-observation-extractor@1.0.10.
• Rosen App and Service2 type checks and installed-export checks passed.
• The PostgreSQL-backed Next build generated all 12 pages and the dynamic API route
  catalogue.
• The September 26 browser exercise confirmed an Ergo order; it did not execute a
  new guard payout. The September 25 four-guard settlement is separate evidence.

Observation identifier checks

Canonical Zcash box:<txid>.<index> values are displayed as input references
in the shared details component, Rosen overview/sidebar, and watcher desktop and
mobile rows. They are not linked as sender addresses. The API field and serialized
event remain unchanged; existing-chain address links are preserved.

Five tests render the actual details and row components. The UI-kit build,
watcher/Rosen application type checks and formatting checks pass, including
independent review. The separate UI-kit-wide type command retains four existing
MenuHandle errors in unchanged SortField/useMenu code.

Coordination

Coordinating review and all seven PRs.

The cross-repository scope and evidence are recorded in the
Zcash integration review.
Merge/release follows official producer packages, regenerated locks, and hosted CI.
Production wallet, contract, token, endpoint, and operator decisions remain open.

The Base proposal in #21 also touches shared network and explorer registries;
its chain implementation is distinct from this Zcash change.