feat: persist photos and enrich conversation history

backend/services/vision.py

@@ -30,8 +30,8 @@ def _require(value: str, label: str) -> str:
     raise ValueError(f"缺少模型资源配置: {label}")
 
 
-def image_data_uri(frame: UserImageRawFrame) -> str:
-    """Encode one Pipecat camera frame for a vision chat-completion request."""
+def image_jpeg_bytes(frame: UserImageRawFrame) -> bytes:
+    """Encode one Pipecat camera frame as a storage- and model-ready JPEG."""
     if not frame.format:
         raise ValueError("摄像头图片帧缺少 format,无法编码给视觉模型")
     buffer = BytesIO()
@@ -40,7 +40,12 @@ def image_data_uri(frame: UserImageRawFrame) -> str:
         format="JPEG",
         quality=85,
     )
-    encoded = base64.b64encode(buffer.getvalue()).decode("utf-8")
+    return buffer.getvalue()
+
+
+def image_data_uri(frame: UserImageRawFrame) -> str:
+    """Encode one Pipecat camera frame for a vision chat-completion request."""
+    encoded = base64.b64encode(image_jpeg_bytes(frame)).decode("utf-8")
     return f"data:image/jpeg;base64,{encoded}"