feat: add filename support to multi-modal prompt messages (#24777)

api/core/file/file_manager.py

         "url": _to_url(f) if dify_config.MULTIMODAL_SEND_FORMAT == "url" else "",
         "format": f.extension.removeprefix("."),
         "mime_type": f.mime_type,
+        "filename": f.filename or "",
     }
     if f.type == FileType.IMAGE:
         params["detail"] = image_detail_config or ImagePromptMessageContent.DETAIL.LOW

api/core/model_runtime/entities/message_entities.py

     base64_data: str = Field(default="", description="the base64 data of multi-modal file")
     url: str = Field(default="", description="the url of multi-modal file")
     mime_type: str = Field(default=..., description="the mime type of multi-modal file")
+    filename: str = Field(default="", description="the filename of multi-modal file")
 
     @property
     def data(self):