feat(media): 作品保存恢复 - 按原任务重试交付并避免重复生成计费

backend/internal/database/task_media_recovery_test.go

@@ -0,0 +1,38 @@
+package database
+
+import (
+	"infinite-canvas/backend/internal/model"
+	"testing"
+)
+
+func TestTaskMediaRecoveryMigrationPreservesHistoricalTasks(t *testing.T) {
+	db, err := Open(Config{Driver: "sqlite", DSN: ":memory:"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	sqlDB, _ := db.DB()
+	t.Cleanup(func() { _ = sqlDB.Close() })
+	if err := db.Exec(`CREATE TABLE tasks (id TEXT PRIMARY KEY, status TEXT, error TEXT)`).Error; err != nil {
+		t.Fatal(err)
+	}
+	if err := db.Exec(`INSERT INTO tasks VALUES ('old-task', 'failed', 'download failed')`).Error; err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 2; i++ {
+		if err := schemaMigrations[33].apply(db); err != nil {
+			t.Fatal(err)
+		}
+	}
+	var task model.Task
+	if err := db.First(&task, "id = ?", "old-task").Error; err != nil {
+		t.Fatal(err)
+	}
+	if task.Status != model.TaskStatusFailed || task.Error != "download failed" || task.MediaRecoveryJSON != "" || task.MediaStage != "" {
+		t.Fatalf("migration rewrote historical task: %+v", task)
+	}
+	for _, field := range []string{"media_stage", "media_recovery_json"} {
+		if !db.Migrator().HasColumn(&model.Task{}, field) {
+			t.Fatalf("missing %s", field)
+		}
+	}
+}