Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@src/services/aws_kms/mod.rs`:
- Around line 931-944: The test test_kms_client_creation_returns_error_not_panic
currently sets AwsKmsSignerConfig.region to None which triggers
resolve_aws_region() and yields AwsKmsError::ConfigError before reaching
Client::new()/catch_unwind; change the test to provide a concrete region (e.g.,
Some("us-west-2".to_string())) on AwsKmsSignerConfig so resolve_aws_region is
bypassed, rename the test to reflect it verifies panic-to-error conversion, call
get_or_create_kms_client(&config).await, and tighten the assertion to
assert!(matches!(result, Err(e) if !matches!(e, AwsKmsError::ConfigError(_))))
or assert the specific error variant produced by the
catch_unwind/panic-conversion branch to ensure the new path is exercised.

In `@src/services/client_cache.rs`:
- Line 10: Update the public docs in src/services/client_cache.rs (e.g., the
module-level comment and the doc comments for the ClientCache type and its
get_or_try_init() method) to reflect the actual contract: there is at most one
in-flight initializer per key under concurrent access, but initializers that
return Err are retried on subsequent calls (so initialization is not strictly
"exactly once" on failures). Add or replace the existing non-document-comments
with /// doc comments on all public items referenced in the review (module,
ClientCache, get_or_try_init(), and any other public functions around lines
noted) to state this behavior clearly and precisely.

In `@src/services/provider/solana/mod.rs`:
- Around line 63-64: The cache used for RPC clients (SOLANA_RPC_CLIENT_CACHE /
STELLAR_RPC_CLIENT_CACHE built from SyncClientCache) blocks the Tokio executor
because initialize_provider() is called from async retry_rpc_call() via
get_provider() -> provider_initializer; replace the blocking SyncClientCache
with an async-aware solution (e.g., use a tokio::sync::RwLock-wrapped map or an
async cache crate) so get_or_try_init-style initialization does not take a
std::sync::Mutex in async contexts, or alternatively move the blocking
initialization into tokio::task::spawn_blocking() inside initialize_provider()
to ensure RPC client creation does not block the executor. Ensure references to
SyncClientCache, SOLANA_RPC_CLIENT_CACHE, STELLAR_RPC_CLIENT_CACHE,
retry_rpc_call, get_provider, provider_initializer, and initialize_provider are
updated accordingly.

In `@src/services/provider/stellar/mod.rs`:
- Around line 420-424: The error path currently includes the raw RPC URL in the
ProviderError (in the STELLAR_RPC_CLIENT_CACHE.get_or_try_init closure that
calls Client::new and maps errors to ProviderError::NetworkConfiguration);
replace the raw `url` with a redacted form by calling
`normalize_url_for_log(url)` (or a local `let redacted =
normalize_url_for_log(url)` and use `redacted` inside the map_err message) so
sensitive userinfo/query tokens are not leaked in logs/telemetry.

---

Nitpick comments:
In `@src/services/client_cache.rs`:
- Around line 31-38: The impl for AsyncClientCache unnecessarily requires K:
Clone—remove the Clone bound from the impl generics (change impl<K: Eq + Hash +
Clone, V> AsyncClientCache<K, V> to impl<K: Eq + Hash, V> AsyncClientCache<K,
V>) and likewise remove Clone from any other AsyncClientCache impl blocks and
method signatures (e.g., the impls that include get_or_try_init and related
methods referenced in the comment) so keys are not constrained to Clone when not
cloned; ensure only Eq + Hash are required in all AsyncClientCache impl blocks
and method headers.

In `@src/services/signer/stellar/aws_kms_signer.rs`:
- Around line 209-223: Add a regression test in this module that exercises the
OnceCell cached path by calling Signer::get_signature_hint() (or the relevant
method that uses self.cached_hint) twice and verifying the mocked
aws_kms_service.get_stellar_address() was invoked exactly once (use
expect_get_stellar_address().times(1) on the mock). The test should initialize
the signer with a mocked aws_kms_service that returns a known address, call
get_signature_hint() twice, assert both calls return the same hint, and assert
the mock's times(1) expectation to ensure no second KMS round-trip occurs.

In `@src/services/signer/stellar/google_cloud_kms_signer.rs`:
- Around line 215-236: Add a regression test that calls get_signature_hint()
twice to verify caching: mock GoogleCloudKmsStellarService::get_stellar_address
(or the test mock helper using expect_get_stellar_address()) to return the
address once and assert it is invoked exactly once (e.g., .times(1)), then call
signer.get_signature_hint().await twice and assert both results are equal; this
ensures cached_hint is reused and protects the behavior of cached_hint,
get_signature_hint, and the interaction with get_stellar_address.