fix(loyalty): correct stamp accumulation, one-per-day guard, and test coverage

- Handler: apply existing redemption BEFORE incrementing stamps (was creating
  and applying redemption to same booking)
- Handler: guard stamp increment behind bookingTotal > 0 (free bookings don't
  earn stamps)
- Handler: fix global milestone off-by-one (globalCount already includes
  current booking since status updated before discount logic)
- Schema: chk_milestone constraint only requires milestone_unit for anniversary
  type, not per_user_booking_count or global_booking_count
- Tests: rewrite from scratch with 12 focused tests:
  - FullCycle, ExistingRedemptionApplies, OneStampPerDay, ZeroTotalNoStamp,
    CycleRepeats, TimeBasedCampaign, PerUserMilestone, GlobalMilestone,
    AnniversaryMilestone, LoyaltyPriority, NoDiscountOnZeroTotal,
    CampaignMaxRedemptions
- Tests: fix path parameter extraction in makeProgressRequest
- Vendor: go mod tidy + vendor for testify dependency

backend/go.sum

@@ -36,6 +36,7 @@ github.com/aws/aws-sdk-go-v2/service/sts v1.41.6 h1:5fFjR/ToSOzB2OQ/XqWpZBmNvmP/
 github.com/aws/aws-sdk-go-v2/service/sts v1.41.6/go.mod h1:qgFDZQSD/Kys7nJnVqYlWKnh0SSdMjAi0uSwON4wgYQ=
 github.com/aws/smithy-go v1.24.1 h1:VbyeNfmYkWoxMVpGUAbQumkODcYmfMRfZ8yQiH30SK0=
 github.com/aws/smithy-go v1.24.1/go.mod h1:LEj2LM3rBRQJxPZTB4KuzZkaZYnZPnvgIhb4pu07mx0=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -63,6 +64,10 @@ github.com/kovidgoyal/go-shm v1.0.0 h1:HJEel9D1F9YhULvClEHJLawoRSj/1u/EDV7MJbBPg
 github.com/kovidgoyal/go-shm v1.0.0/go.mod h1:Yzb80Xf9L3kaoB2RGok9hHwMIt7Oif61kT6t3+VnZds=
 github.com/kovidgoyal/imaging v1.8.19 h1:zWJdQqF2tfSKjvoB7XpLRhVGbYsze++M0iaqZ4ZkhNk=
 github.com/kovidgoyal/imaging v1.8.19/go.mod h1:I0q8RdoEuyc4G8GFOF9CaluTUHQSf68d6TmsqpvfRI8=
+github.com/kr/pretty v0.3.0 h1:WgNl7dwNpEZ6jJ9k1snq4pZsg7DOEN8hP9Xw0Tsjwk0=
+github.com/kr/pretty v0.3.0/go.mod h1:640gp4NfQd8pI5XOwp5fnNeVWj67G7CFk/SaSQn7NBk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/lestrrat-go/blackmagic v1.0.4 h1:IwQibdnf8l2KoO+qC3uT4OaTWsW7tuRQXy9TRN9QanA=
 github.com/lestrrat-go/blackmagic v1.0.4/go.mod h1:6AWFyKNNj0zEXQYfTMPfZrAXUWUfTIZ5ECEUEJaijtw=
 github.com/lestrrat-go/httpcc v1.0.1 h1:ydWCStUeJLkpYyjLDHihupbn2tYmZ7m22BGkcvZZrIE=
@@ -83,6 +88,8 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/robfig/cron/v3 v3.0.1 h1:WdRxkvbJztn8LMz/QEvLN5sBU+xKpSqwwUO1Pjr4qDs=
 github.com/robfig/cron/v3 v3.0.1/go.mod h1:eQICP3HwyT7UooqI/z+Ov+PtYAWygg1TEWWzGIFLtro=
+github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
+github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
 github.com/rwcarlsen/goexif v0.0.0-20190401172101-9e8deecbddbd h1:CmH9+J6ZSsIjUK3dcGsnCnO41eRBOnY12zwkn5qVwgc=
 github.com/rwcarlsen/goexif v0.0.0-20190401172101-9e8deecbddbd/go.mod h1:hPqNNc0+uJM6H+SuU8sEs5K5IQeKccPqeSjfgcKGgPk=
 github.com/segmentio/asm v1.2.1 h1:DTNbBqs57ioxAD4PrArqftgypG4/qNpXoJx8TVXxPR0=
@@ -109,6 +116,8 @@ golang.org/x/text v0.34.0/go.mod h1:homfLqTYRFyVYemLBFl5GgL/DWEiH5wcsQ5gSh1yziA=
 google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
 google.golang.org/protobuf v1.36.11/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=