refactor(structure): group platform, infra, and shared packages

Move process wiring, technical adapters, and cross-cutting contracts out of flat internal/ packages so new code has a clear home without changing business layout.

internal/testhelper/gin.go

@@ -4,7 +4,7 @@
 package testhelper
 
 import (
-	"github.com/Rain-kl/Wavelet/internal/common/response"
+	"github.com/Rain-kl/Wavelet/internal/shared/response"
 	"github.com/gin-gonic/gin"
 )
 

internal/testhelper/test_helper.go

@@ -9,7 +9,7 @@ import (
 	"context"
 	"testing"
 
-	"github.com/Rain-kl/Wavelet/internal/db"
+	"github.com/Rain-kl/Wavelet/internal/infra/persistence"
 	"github.com/Rain-kl/Wavelet/internal/model"
 	"github.com/Rain-kl/Wavelet/internal/repository"
 	"github.com/alicebob/miniredis/v2"