fix(tempo/server): log tx hash + receipt detail on chain reverts

The patched chargeserver.verifyTransaction currently swallows the
underlying tx hash on broadcast and the revert reason on a non-0x1
receipt. Operators investigating "transaction reverted" failures have
no way to inspect the failed tx without code-level instrumentation.
This is the same diagnostic gap PR #34 (this PR) closed for the
keychain signature path; extending it to broadcast/receipt:

  - Log txHash on successful broadcast (and on SendRawTransaction
    failure, with the underlying error).
  - On a non-0x1 receipt: log status / blockNumber / gasUsed /
    revertReason and the full receipt map. Surface the revert
    reason in the response body when the chain provides one.
  - Log fetchReceipt errors with the txHash for context.

Receipt bodies are chain-public; no secrets exposed. Production cost
is one extra log line per successful broadcast plus a multi-field log
on failure.

Mirrored from blockparty-global/sre-services PR #190 + #194.

Author: jake-bp

pkg/tempo/server/charge.go

@@ -451,10 +451,13 @@ func (i *Intent) verifyTransaction(
 
 	txHash, err := rpc.SendRawTransaction(ctx, serialized)
 	if err != nil {
-		return nil, mpp.ErrVerificationFailed("transaction submission failed")
+		log.Printf("[mpp] verifyTransaction: SendRawTransaction failed: %v", err)
+		return nil, mpp.ErrVerificationFailed(fmt.Sprintf("transaction submission failed: %v", err))
 	}
+	log.Printf("[mpp] verifyTransaction: tx broadcast: hash=%s", txHash)
 	receiptMap, err := fetchReceipt(ctx, rpc, txHash)
 	if err != nil {
+		log.Printf("[mpp] verifyTransaction: fetchReceipt failed: %v (hash=%s)", err, txHash)
 		return nil, err
 	}
 	if !receiptMatches(receiptMap, credential, request, sender.Hex()) {
@@ -539,7 +542,20 @@ func fetchReceipt(ctx context.Context, rpc tempo.RPCClient, hash string) (map[st
 		if receipt, ok := response.Result.(map[string]any); ok && len(receipt) > 0 {
 			status := asString(receipt["status"])
 			if status != "0x1" {
-				return nil, mpp.ErrVerificationFailed("transaction reverted")
+				// Surface the on-chain revert reason. Tempo's eth_getTransactionReceipt
+				// includes status, gasUsed, blockNumber, and any revert reason the chain
+				// chooses to return. Logging the whole receipt (other than logs[]) gives
+				// us deterministic context the next time we hit a chain revert.
+				rev := asString(receipt["revertReason"])
+				blk := asString(receipt["blockNumber"])
+				gas := asString(receipt["gasUsed"])
+				log.Printf("[mpp] fetchReceipt: tx reverted: hash=%s status=%s blockNumber=%s gasUsed=%s revertReason=%q full_receipt=%+v",
+					hash, status, blk, gas, rev, receipt)
+				detail := "transaction reverted"
+				if rev != "" {
+					detail = fmt.Sprintf("transaction reverted: %s", rev)
+				}
+				return nil, mpp.ErrVerificationFailed(detail)
 			}
 			return receipt, nil
 		}