perf(subgraph): migrate weekly/monthly activity metrics to native timeseries + @aggregation

[silent-cipher]

Problem

Almost every handler ends with a metrics fan-out via subgraph/src/helper.ts: saveProviderMetrics ×2 (weekly + monthly) + saveProofSetMetrics ×2 + saveNetworkMetrics. Each is a read-modify-write on a mutable entity, so a single on-chain event produces ~5 extra store reads and ~5 new mutable row versions — the single largest write amplifier in the subgraph. The NetworkMetric singleton in particular gets a new row version for nearly every event. The generic store.get/Entity/Value plumbing with toHexString() string keys adds overhead on top.

Proposal

We're on specVersion 1.3.0, so graph-node native aggregations are available:

• Define timeseries entities (@entity(timeseries: true), id: Int8!, timestamp: Timestamp!) for provider activity and dataset activity data points. Handlers append one immutable point instead of 4 read-modify-writes; graph-node rolls up buckets in Postgres at interval boundaries.
• Define @aggregation(intervals: ["hour", "day"], source: ...) entities with@aggregate(fn: "sum", arg: ...) for the existing counters (rootsAdded/removed, dataSize, proofs, faults, …).
• Replace NetworkMetric running totals with cumulative: true aggregates from the same source, removing the singleton churn.
• Delete helper.ts (saveProviderMetrics / saveProofSetMetrics / saveNetworkMetrics) once migrated.

Constraints / client impact

• Aggregation intervals are hour/day only — no native week/month. The client (subgraph-client/src/utility/queries.ts: weeklyProviderActivities, weeklyProofSetActivities, monthlyProofSetActivities, networkMetricsQuery) must sum daily buckets into weeks/months, or we keep a thin weekly/monthly layer and only migrate the network totals.
• Full resync + coordinated client release required.

Acceptance criteria

• Schema design reviewed (entity + aggregation definitions) before implementation
• Handlers perform at most 1 metrics write per event (immutable append)
• Client charts/stat tiles render identically against the new schema

Reference

https://thegraph.com/docs/en/subgraphs/best-practices/timeseries