feat: 添加图片生成功能及相关配置

- 添加图片生成相关配置和环境变量
- 新增图片上传服务和模型定义
- 扩展模型服务以支持图片生成模型
- 添加图片生成响应处理器
- 更新README文档以反映新功能
- 添加GitHub Actions发布工作流

app/schemas/image_models.py

@@ -0,0 +1,23 @@
+class ImageMetadata:
+    def __init__(self, width: int, height: int, filename: str, size: int, url: str, delete_url: str | None = None):
+        self.width = width
+        self.height = height
+        self.filename = filename
+        self.size = size
+        self.url = url
+        self.delete_url = delete_url
+    
+    
+class UploadResponse:
+    def __init__(self, success: bool, code: str, message: str, data: ImageMetadata):
+        self.success = success
+        self.code = code
+        self.message = message
+        self.data = data
+    
+    
+class ImageUploader:
+    def upload(self, file: bytes, filename: str) -> UploadResponse:
+        raise NotImplementedError
+    
+