fix(bitcoin-da): return MempoolSpaceRequestError on HTTP failure in get_fee_rate_from_mempool_space

[amathxbt]

Summary

get_fee_rate_from_mempool_space maps a network-level reqwest::Error (timeout, connection refused, DNS failure, etc.) to FeeServiceError::MempoolSpaceParseError instead of FeeServiceError::MempoolSpaceRequestError.

Bug

let response = get_with_timeout(url.clone(), MEMPOOL_SPACE_TIMEOUT)
    .await
    .map_err(|e| {
        trace!("Failed to fetch from {}: {:?}", url, e);
        FeeServiceError::MempoolSpaceParseError   // ← wrong variant
    })?;

MempoolSpaceParseError is intended for JSON deserialization failures. Using it here:

1. Misleads callers and log readers who see a "parse error" for what is really a connectivity issue.
2. Wastes the existing #[from] reqwest::Error impl on MempoolSpaceRequestError, which was added precisely for this case.

Fix

Use the correct variant so the two failure modes are distinguishable:

.map_err(|e| {
    trace!("Failed to fetch from {}: {:?}", url, e);
    FeeServiceError::MempoolSpaceRequestError(e)  // ← correct
})?;

Files changed

• crates/bitcoin-da/src/fee.rs

[amathxbt]

@jfldde @eyusufatik — this PR is approved and ready. No lint issues found. Pinging for merge.