perf(bridge): fetch transaction operations once in processTransaction (#1098)

When a Stellar transaction credited the bridge account more than once,
processTransaction called getOperationEffect(tx.Hash) once per matching
account_credited effect, refetching identical operation data from Horizon
each time and slowing down processing.

Fetch the operations lazily at most once per transaction and reuse the
result across all matching effects. The fetch still happens only when a
matching TFT credit is present (no extra call for unrelated transactions),
and per-effect MintEvent emission is unchanged, so behaviour is preserved.

Closes #1051

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: sameh-farouk

bridge/tfchain_bridge/pkg/stellar/stellar.go

@@ -502,6 +502,13 @@ func (w *StellarWallet) processTransaction(tx hProtocol.Transaction) ([]MintEven
 	asset := w.getAssetCodeAndIssuer()
 
 	var mintEvents []MintEvent
+	// A transaction's operations are identical no matter how many times the bridge
+	// account is credited within it, so fetch them at most once and reuse the result
+	// across all matching account_credited effects. Previously this Horizon call was
+	// made once per matching effect, refetching the same data when a single
+	// transaction credited the bridge more than once (#1051).
+	var ops operations.OperationsPage
+	opsFetched := false
 	for _, effect := range effects.Embedded.Records {
 		if effect.GetAccount() != w.config.StellarBridgeAccount {
 			continue
@@ -520,9 +527,12 @@ func (w *StellarWallet) processTransaction(tx hProtocol.Transaction) ([]MintEven
 			continue
 		}
 
-		ops, err := w.getOperationEffect(tx.Hash)
-		if err != nil {
-			continue
+		if !opsFetched {
+			ops, err = w.getOperationEffect(tx.Hash)
+			if err != nil {
+				continue
+			}
+			opsFetched = true
 		}
 
 		senders := make(map[string]*big.Int)