[P2-E7.3] Operator metrics & dashboards

**Context.** Operating the loop needs: reconciliation lag (purchase seen → limit set),
per-member traffic balances vs limits, fee runway (`paidThrough - now`), report cadence
compliance.

**Deliverable.** Metrics in the operator app (P2-E5.2) + a reference dashboard; alert
rules for reconciliation stall, fee lapse approaching, report overdue.

**Acceptance.** Dashboard renders against LocalNet; each alert fires under its synthetic
condition.

**Depends on.** P2-E5.3, P2-E3.1, P2-E6.1.

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Epic: #70 · Plan: [P2-E7-scan.md](https://github.com/ChainSafe/canton-extending-mainnet/blob/main/docs/planning/phase-2-epics/P2-E7-scan.md)

Start with the operator app work in P2-E5.2 and review the dependent items P2-E5.3, P2-E3.1, and P2-E6.1, along with the P2-E7 scan plan. Confirm how metrics and alert rules are represented, then validate the reference dashboard against LocalNet and verify each alert fires under its synthetic condition.

Written by the indexing model from the issue text.