feat(settlement): add metrics + Grafana panels for the settlement service

[kariy]

Summary

Adds Prometheus metrics to the embedded settlement service, plus a Settlement row on the Grafana overview dashboard. The headline metric is proof-generation time, with other settlement stages and outcomes tracked alongside.

Metrics (katana_settlement_*)

Instrumented at the service layer so they are agnostic to the proving backend:

Metric	Type	Measures
proof_generation_seconds	Histogram	Backend prove() — attestation build + proving (the dominant cost)
settle_batch_seconds	Histogram	End-to-end settle (prove + submit)
state_update_seconds	Histogram	update_state tx submit + confirmation
blocks_per_batch	Histogram	Blocks per settled batch
batches_settled_total / blocks_settled_total	Counter	Settlement throughput
settlement_failures_total	Counter	Failed attempts (each triggers backoff + retry)
settled_block	Gauge	Current on-chain settlement cursor

The two proof-related timings carry a proof_type label (sp1 / mock) via a new ProvingBackend::proof_type(), so they can be broken down and compared across backends.

Because the global Prometheus recorder is already installed at node startup, these auto-register on the existing metrics endpoint — no additional wiring.

Dashboard

A 7-panel Settlement row in monitoring/grafana/dashboards/overview.json. Duration panels read the exporter's summary quantile labels directly (p50/p90/p99), matching the existing RPC-latency panels. Inserted as pure additions with no reformatting of existing panels.

Checks

• cargo +nightly-2025-02-20 fmt --all — clean
• clippy (-p katana-settlement --all-targets with the repo's deny flags) — clean

🤖 Generated with Claude Code

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.30.

Benchmark suite	Current: 32df2a5	Previous: bbe2576	Ratio
FinalityStatus/compress	1 ns/iter (± 0)	0 ns/iter (± 0)	+∞
TypedTransactionExecutionInfo/decompress	3581 ns/iter (± 64)	2673 ns/iter (± 149)	1.34
TrieHistoryEntry/decompress	260 ns/iter (± 11)	183 ns/iter (± 16)	1.42

This comment was automatically generated by workflow using github-action-benchmark.

CC: @kariy

[github-actions]

Codec benchmark diff vs main

Benchmark	Baseline (ns)	Current (ns)	Δ
CompiledClass(fixture)/compress	2485031	2679052	+7.81%
CompiledClass(fixture)/decompress	2624721	2803165	+6.80%
ExecutionCheckpoint/compress	27	31	+14.81%
ExecutionCheckpoint/decompress	23	23	+0.00%
PruningCheckpoint/compress	27	31	+14.81%
PruningCheckpoint/decompress	23	23	+0.00%
VersionedHeader/compress	623	605	-2.89%
VersionedHeader/decompress	744	839	+12.77%
StoredBlockBodyIndices/compress	70	74	+5.71%
StoredBlockBodyIndices/decompress	36	34	-5.56%
StorageEntry/compress	122	143	+17.21%
StorageEntry/decompress	118	142	+20.34%
ContractNonceChange/compress	123	145	+17.89%
ContractNonceChange/decompress	204	233	+14.22%
ContractClassChange/compress	167	183	+9.58%
ContractClassChange/decompress	219	252	+15.07%
ContractStorageEntry/compress	131	152	+16.03%
ContractStorageEntry/decompress	281	331	+17.79%
GenericContractInfo/compress	116	129	+11.21%
GenericContractInfo/decompress	83	104	+25.30%
Felt/compress	69	80	+15.94%
Felt/decompress	45	55	+22.22%
BlockHash/compress	69	80	+15.94%
BlockHash/decompress	45	58	+28.89%
TxHash/compress	72	80	+11.11%
TxHash/decompress	46	55	+19.57%
ClassHash/compress	70	80	+14.29%
ClassHash/decompress	45	55	+22.22%
CompiledClassHash/compress	69	80	+15.94%
CompiledClassHash/decompress	45	55	+22.22%
BlockNumber/compress	43	47	+9.30%
BlockNumber/decompress	23	24	+4.35%
TxNumber/compress	42	47	+11.90%
TxNumber/decompress	23	24	+4.35%
FinalityStatus/compress	0	1	+Infinity%
FinalityStatus/decompress	9	10	+11.11%
TypedTransactionExecutionInfo/compress	14558	16094	+10.55%
TypedTransactionExecutionInfo/decompress	2673	3581	+33.97%
VersionedContractClass/compress	366	380	+3.83%
VersionedContractClass/decompress	654	797	+21.87%
MigratedCompiledClassHash/compress	117	143	+22.22%
MigratedCompiledClassHash/decompress	117	139	+18.80%
ContractInfoChangeList/compress	1490	1360	-8.72%
ContractInfoChangeList/decompress	2050	2102	+2.54%
BlockChangeList/compress	645	586	-9.15%
BlockChangeList/decompress	844	845	+0.12%
ReceiptEnvelope/compress	25381	29965	+18.06%
ReceiptEnvelope/decompress	5335	6114	+14.60%
TrieDatabaseValue/compress	138	165	+19.57%
TrieDatabaseValue/decompress	229	234	+2.18%
TrieHistoryEntry/compress	248	281	+13.31%
TrieHistoryEntry/decompress	183	260	+42.08%

[github-actions]

Runner: AMD EPYC 7763 64-Core Processor (4 cores) · 15Gi RAM

[codecov]

Codecov Report

❌ Patch coverage is 0% with 26 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.11%. Comparing base (9bde0ae) to head (32df2a5).
⚠️ Report is 482 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/settlement/src/service.rs	0.00%	21 Missing ⚠️
crates/settlement/src/backend/tee/mod.rs	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #625      +/-   ##
==========================================
- Coverage   73.32%   68.11%   -5.21%     
==========================================
  Files         209      333     +124     
  Lines       23132    46615   +23483     
==========================================
+ Hits        16961    31751   +14790     
- Misses       6171    14864    +8693     

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