feat(admin): establish core data model

admin/internal/domain/spec_trial.go

@@ -0,0 +1,16 @@
+package domain
+
+import "time"
+
+type SpecTrial struct {
+	ID             string
+	TaskID         string
+	Attempt        int
+	ProductTitle   string
+	SelectedColor  string
+	SelectedSize   string
+	UnitPrice      string
+	TotalPrice     string
+	EvidenceSHA256 string
+	CreatedAt      time.Time
+}