Port bundled MINIO Grafana dashboards and alert rules to Metrics V3

Parent: #763

Problem

Switching ingestion to Metrics V3 is incomplete while Pigsty's bundled Grafana dashboards and VictoriaMetrics alert rules still query V2 metric names and assumptions. V3 changes names, labels, units, and in some cases the scrape/duplication model.

Scope

Audit and port every shipped MINIO consumer, including at least:

• files/grafana/minio/minio-overview.json
• files/grafana/minio/minio-instance.json
• MINIO panels embedded in files/grafana/pigsty.json and related overview dashboards
• files/victoria/rules/minio.yml

Use native V3 names and semantics. Do not perform a blind text rename:

• map changed label keys, including API/operation labels;
• correct rate windows and byte/second units;
• handle cluster-wide gauges that are repeated by node scrapes with min/max or another semantically correct aggregation rather than sum;
• scope cluster views by cls and instance views by ins;
• include configured bucket identity where applicable;
• replace unavailable low-value V2 widgets with actionable V3 health or freshness signals.

The Console-side mapping and Info-page replacement discussions live in:

• pgsty/silo-console#7
• pgsty/silo-console#8

Suggested health coverage

At minimum, preserve or add actionable views/alerts for availability, erasure-set health, offline drives/nodes, capacity pressure, S3 error rate, request latency, replication/healing backlog where present, and usage-data freshness.

Acceptance criteria

• No active SILO dashboard panel or alert rule depends on a V2-only metric name.
• Dashboards work for single-node, distributed, and two-cluster test data.
• Repeated cluster-wide gauges do not inflate totals.
• Dashboard variables and links preserve cls/ ins context.
• Grafana provisioning succeeds and all PromQL expressions parse.
• VictoriaMetrics rule checks pass and representative synthetic failure states trigger/recover as expected.
• Any retained V2 compatibility path is isolated and documented rather than mixed into every V3 query.

Start with the listed MINIO dashboards, embedded panels, and files/victoria/rules/minio.yml, then review parent #763 and the linked console mapping discussions. Audit every V2 metric, label, unit, aggregation, and cls/ins variable before updating the consumers. Done means provisioning and PromQL checks pass, representative failure states trigger and recover, and single-node, distributed, and two-cluster data remain correct.