[P2-E7] Scan & observability

Public, funding-side visibility: registrations, fee states, per-synchronizer purchase
aggregates, and report/burn reconciliation are readable without operating a node.
Consumption details beyond the FR-27 aggregates stay private to the dedicated sync.

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Milestone: Phase 2 · Plan: [P2-E7-scan.md](https://github.com/ChainSafe/canton-extending-mainnet/blob/main/docs/planning/phase-2-epics/P2-E7-scan.md) · Leaves filed as sub-issues.

Start with docs/planning/phase-2-epics/P2-E7-scan.md and review the linked or filed sub-issues for the scan and observability scope. Completion is defined by the requirements and acceptance criteria in that plan and its leaves, including public visibility for the listed aggregates and reconciliation while keeping consumption details private.

Written by the indexing model from the issue text.