feat: support multi-image image generation

apps/api/models.py

@@ -98,3 +98,35 @@ class ImageGenerationTask(models.Model):
 
     def __str__(self) -> str:
         return f"{self.task_id} {self.status}"
+
+
+class ImageGenerationTaskInput(models.Model):
+    task = models.ForeignKey(
+        ImageGenerationTask,
+        verbose_name="图片生成任务",
+        on_delete=models.CASCADE,
+        related_name="input_images",
+    )
+    ordinal = models.PositiveSmallIntegerField("输入顺序")
+    image = models.FileField(
+        "输入图片",
+        upload_to="generated/task_inputs/%Y/%m/%d/",
+    )
+    mime_type = models.CharField("MIME 类型", max_length=100)
+    filename = models.CharField("原始文件名", max_length=255)
+    created_at = models.DateTimeField("创建时间", auto_now_add=True)
+
+    class Meta:
+        db_table = "image_generation_task_input"
+        verbose_name = "图片生成任务输入"
+        verbose_name_plural = "图片生成任务输入"
+        ordering = ("ordinal", "id")
+        constraints = [
+            models.UniqueConstraint(
+                fields=("task", "ordinal"),
+                name="unique_image_task_input_ordinal",
+            )
+        ]
+
+    def __str__(self) -> str:
+        return f"{self.task.task_id} #{self.ordinal + 1}"