refactor(layout): relocate go.mod to backend/ and clean import paths to module root

- Relocated go.mod and go.sum into backend/ root directory
- Stripped redundant backend/ segments from all Go imports (github.com/Rain-kl/Wavelet/...)
- Unified Makefile, swagger, and build-test to execute in backend/ module context
- Ensured 100% build-test, code-check, format, and swagger pass

backend/plugins/drivers/driver_http/engine.go

@@ -16,11 +16,11 @@ import (
 	"syscall"
 	"time"
 
-	"github.com/Rain-kl/Wavelet/backend/pkg/config"
-	"github.com/Rain-kl/Wavelet/backend/pkg/trace"
-	"github.com/Rain-kl/Wavelet/backend/pkg/util"
-	"github.com/Rain-kl/Wavelet/backend/plugins/domain/auth"
-	"github.com/Rain-kl/Wavelet/backend/plugins/domain/risk_control"
+	"github.com/Rain-kl/Wavelet/pkg/config"
+	"github.com/Rain-kl/Wavelet/pkg/trace"
+	"github.com/Rain-kl/Wavelet/pkg/util"
+	"github.com/Rain-kl/Wavelet/plugins/domain/auth"
+	"github.com/Rain-kl/Wavelet/plugins/domain/risk_control"
 	"github.com/gin-contrib/sessions"
 	"github.com/gin-contrib/sessions/redis"
 	"github.com/gin-gonic/gin"

backend/plugins/drivers/driver_http/middlewares.go

@@ -12,11 +12,11 @@ import (
 	"strings"
 	"time"
 
-	"github.com/Rain-kl/Wavelet/backend/pkg/config"
-	"github.com/Rain-kl/Wavelet/backend/pkg/logger"
-	"github.com/Rain-kl/Wavelet/backend/pkg/response"
-	otel_trace "github.com/Rain-kl/Wavelet/backend/pkg/trace"
-	database "github.com/Rain-kl/Wavelet/backend/plugins/infra/database"
+	"github.com/Rain-kl/Wavelet/pkg/config"
+	"github.com/Rain-kl/Wavelet/pkg/logger"
+	"github.com/Rain-kl/Wavelet/pkg/response"
+	otel_trace "github.com/Rain-kl/Wavelet/pkg/trace"
+	database "github.com/Rain-kl/Wavelet/plugins/infra/database"
 	"github.com/gin-gonic/gin"
 	"go.opentelemetry.io/otel/codes"
 	"go.opentelemetry.io/otel/trace"

backend/plugins/drivers/driver_http/middlewares_test.go

@@ -8,7 +8,7 @@ import (
 	"net/http/httptest"
 	"testing"
 
-	"github.com/Rain-kl/Wavelet/backend/pkg/testhelper"
+	"github.com/Rain-kl/Wavelet/pkg/testhelper"
 	"github.com/gin-gonic/gin"
 )
 

backend/plugins/drivers/driver_http/plugin.go

@@ -15,8 +15,8 @@ import (
 
 	"github.com/gin-gonic/gin"
 
-	"github.com/Rain-kl/Wavelet/backend/core"
-	"github.com/Rain-kl/Wavelet/backend/pkg/util"
+	"github.com/Rain-kl/Wavelet/core"
+	"github.com/Rain-kl/Wavelet/pkg/util"
 )
 
 const (