feat: integrate unified payment and wallet refunds

backend/go.work.sum

@@ -4,6 +4,7 @@ cloud.google.com/go/compute/metadata v0.9.0 h1:pDUj4QMoPejqq20dK0Pg2N4yG9zIkYGdB
 cloud.google.com/go/compute/metadata v0.9.0/go.mod h1:E0bWwX5wTnLPedCKqk3pJmVgCBSM6qQI1yTBdEb3C10=
 github.com/GoogleCloudPlatform/opentelemetry-operations-go/detectors/gcp v1.31.0 h1:DHa2U07rk8syqvCge0QIGMCE1WxGj9njT44GH7zNJLQ=
 github.com/GoogleCloudPlatform/opentelemetry-operations-go/detectors/gcp v1.31.0/go.mod h1:P4WPRUkOhJC13W//jWpyfJNDAIpvRbAUIYLX/4jtlE0=
+github.com/agiledragon/gomonkey v2.0.2+incompatible h1:eXKi9/piiC3cjJD1658mEE2o3NjkJ5vDLgYjCQu0Xlw=
 github.com/antihax/optional v1.0.0 h1:xK2lYat7ZLaVVcIuj82J8kIro4V6kDe0AUDFboUCwcg=
 github.com/antihax/optional v1.0.0/go.mod h1:uupD/76wgC+ih3iEmQUL+0Ugr19nfwCT1kdvxnR2qWY=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
@@ -40,6 +41,7 @@ github.com/jordanlewis/gcassert v0.0.0-20250430164644-389ef753e22e h1:a+PGEeXb+e
 github.com/jordanlewis/gcassert v0.0.0-20250430164644-389ef753e22e/go.mod h1:ZybsQk6DWyN5t7An1MuPm1gtSZ1xDaTXS9ZjIOxvQrk=
 github.com/kisielk/errcheck v1.5.0 h1:e8esj/e4R+SAOwFwN+n3zr0nYeCyeweozKfO23MvHzY=
 github.com/kisielk/gotool v1.0.0 h1:AV2c/EiW3KqPNT9ZKl07ehoAGi4C5/01Cfbblndcapg=
+github.com/kisielk/sqlstruct v0.0.0-20201105191214-5f3e10d3ab46 h1:veS9QfglfvqAw2e+eeNT/SbGySq8ajECXJ9e4fPoLhY=
 github.com/klauspost/compress v1.18.5 h1:/h1gH5Ce+VWNLSWqPzOVn6XBO+vJbCNGvjoaGBFW2IE=
 github.com/klauspost/compress v1.18.5/go.mod h1:cwPg85FWrGar70rWktvGQj8/hthj3wpl0PGDogxkrSQ=
 github.com/mattn/go-sqlite3 v1.14.22 h1:2gZY6PC6kBnID23Tichd1K+Z0oS6nE/XwU+Vz/5o4kU=