Add detailed backup notifications

internal/service/notification_test.go

@@ -0,0 +1,21 @@
+package service
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/backupper-unraid/backupper/internal/model"
+)
+
+func TestNotificationMessageIncludesBackupStatistics(t *testing.T) {
+	started := time.Date(2026, 6, 14, 12, 0, 0, 0, time.UTC)
+	finished := started.Add(2*time.Minute + 8*time.Second)
+	run := model.Run{TaskType: "backup", Status: "success", StartedAt: &started, FinishedAt: &finished, SnapshotID: "abc123", BytesAdded: 1536, FilesNew: 7, FilesChanged: 2, BytesProcessed: 5 * 1024 * 1024, FilesProcessed: 120}
+	message := notificationMessage(run, finished)
+	for _, expected := range []string{"Status: Erfolgreich", "Dauer: 2 Min. 8 Sek.", "Neu gespeichert: 1.5 KiB", "Neue Dateien: 7", "Geänderte Dateien: 2", "Gesamtgröße dieses Backups: 5.0 MiB", "Dateien insgesamt: 120", "Snapshot: abc123"} {
+		if !strings.Contains(message, expected) {
+			t.Errorf("message %q does not contain %q", message, expected)
+		}
+	}
+}