[P2-E5] Sync Operator Node & reconciliation

The operator-side runtime: a dual-homed deployment (participant on both the global and the
dedicated synchronizer) that watches on-ledger purchases for its synchronizer and turns
them into enforced sequencer traffic limits on the dedicated synchronizer
(`SetTrafficPurchased`), with the sequencer's free base rate set to zero so the burn is
the only source of capacity. Splice surface: the SV app's existing
reconciliation/merge/top-up triggers generalize; the operator node reuses them against its
own sequencer.

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Milestone: Phase 2 · Plan: [P2-E5-operator-node.md](https://github.com/ChainSafe/canton-extending-mainnet/blob/main/docs/planning/phase-2-epics/P2-E5-operator-node.md) · Leaves filed as sub-issues.