feat(metrics): add value pool, RPC, and peer health metrics (ZcashFoundation#10175)

* feat(metrics): add value pool, RPC, and peer health metrics

Add Prometheus metrics for operational visibility:

- Value pool metrics: transparent, sprout, sapling, orchard, deferred
  balances and total chain supply (zebra-state)
- RPC metrics middleware: request counts, latencies, active requests,
  and errors per method (zebra-rpc)
- Peer handshake metrics: duration histograms and failure tracking
  by reason (zebra-network)

Also includes:
- Grafana dashboards for value pools and RPC monitoring
- Prometheus alert rules for critical conditions
- Updated CHANGELOG

Closes ZcashFoundation#10162, closes ZcashFoundation#10163, closes ZcashFoundation#10164, closes ZcashFoundation#10167

* chore: remove wrongly commited files to `.gitignore`

* chore: cargo fmt

* chore: clippy fix

* docs: fix changelog entries for PR ZcashFoundation#10175

- Remove ZcashFoundation#10174 entries from [Unreleased] (already in 4.0.0)
- Remove redundant "Added" prefix from entries
- Link to PR ZcashFoundation#10175 instead of issues
- Add rpc_metrics module entry to zebra-rpc changelog

* Update CHANGELOG.md

Co-authored-by: Marek <mail@marek.onl>

* Update zebra-rpc/CHANGELOG.md

Co-authored-by: Marek <mail@marek.onl>

---------

Co-authored-by: Marek <mail@marek.onl>

Author: gustavovalverde

.gitignore

@@ -1,5 +1,3 @@
-docs/
-!docs/**/*.md
 # Cargo files
 /coverage-target/
 # Legacy Zebra state (alpha versions only)

CHANGELOG.md

@@ -53,9 +53,9 @@ Thank you to everyone who contributed to this release, we couldn't make Zebra wi
 
 ### Added
 
-- OpenTelemetry tracing support behind the `opentelemetry` feature flag ([#10174](https://github.com/ZcashFoundation/zebra/pull/10174))
-- RPC tracing middleware with `SPAN_KIND_SERVER` spans for Jaeger Service Performance Monitoring ([#10174](https://github.com/ZcashFoundation/zebra/pull/10174))
-- Added Docker Compose observability stack with Jaeger, Prometheus, Grafana, and AlertManager for local development and testing
+- Value pool metrics exposing transparent, sprout, sapling, orchard, and deferred pool balances plus total chain supply ([#10175](https://github.com/ZcashFoundation/zebra/pull/10175))
+- Peer handshake metrics for duration histograms and failure tracking by reason ([#10175](https://github.com/ZcashFoundation/zebra/pull/10175))
+- Prometheus alert rules and Grafana dashboards for value pools and RPC monitoring ([#10175](https://github.com/ZcashFoundation/zebra/pull/10175))
 
 
 ## [Zebra 3.1.0](https://github.com/ZcashFoundation/zebra/releases/tag/v3.1.0) - 2025-11-28

Cargo.lock

@@ -7158,6 +7158,7 @@ dependencies = [
  "jsonrpsee",
  "jsonrpsee-proc-macros",
  "jsonrpsee-types",
+ "metrics",
  "nix",
  "proptest",
  "prost 0.14.3",