chore(v2): 终审收尾——settle-sync 非常态结果落日志 + Retry 补 body 上限

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nMthbVEmQquxBRKb9Fj8u

internal/gateway/settle.go

@@ -3,6 +3,7 @@ package gateway
 import (
 	"context"
 	"errors"
+	"log"
 	"time"
 
 	"github.com/wangjia/pay/internal/model"
@@ -131,8 +132,14 @@ func (g *Gateway) SyncPendingAttempts(ctx context.Context, limit int) (int, erro
 		if err != nil || ev == nil {
 			continue
 		}
-		if res, _ := g.Settle(ctx, ev); res == SettleProcessed {
+		res, serr := g.Settle(ctx, ev)
+		switch res {
+		case SettleProcessed:
 			settled++
+		case SettleIgnored, SettleDuplicate:
+			// 常态:未付/已处理,不刷日志
+		default: // not_found / amount_mismatch / failed —— 对账兜底的盲区,必须可见
+			log.Printf("[settle-sync] attempt=%s channel=%s result=%s err=%v", att.ProviderRef, att.Channel, res, serr)
 		}
 	}
 	return settled, nil