refactor: replace print() with structured logging across backend

Replace all print()/stderr logging with Python logging module using
logger = logging.getLogger(__name__) pattern for consistent log levels
and formatting. Extract score conversion to shared score_utils module.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/services/image_generation_service.py

@@ -4,12 +4,15 @@
 """
 
 import base64
+import logging
 import uuid
 from pathlib import Path
 from typing import Dict, Any
 import httpx
 from src.core.config import settings
 
+logger = logging.getLogger(__name__)
+
 
 class ImageGenerationService:
     """统一的图像生成服务基类"""
@@ -21,9 +24,9 @@ class ImageGenerationService:
     
     async def call_api(self, model: str, payload: dict) -> dict:
         """调用硅基流动 API"""
-        print(f"[DEBUG] 调用SiliconFlow API: {self.base_url}")
-        print(f"[DEBUG] 模型: {model}")
-        print(f"[DEBUG] 请求参数: {payload}")
+        logger.debug(f"调用SiliconFlow API: {self.base_url}")
+        logger.debug(f"模型: {model}")
+        logger.debug(f"请求参数: {payload}")
         
         async with httpx.AsyncClient(timeout=self.timeout) as client:
             response = await client.post(
@@ -37,9 +40,9 @@ class ImageGenerationService:
             response.raise_for_status()
             
             result = response.json()
-            print(f"[DEBUG] API响应状态: {response.status_code}")
-            print(f"[DEBUG] API响应类型: {type(result)}")
-            print(f"[DEBUG] API响应键: {list(result.keys()) if isinstance(result, dict) else '非字典类型'}")
+            logger.debug(f"API响应状态: {response.status_code}")
+            logger.debug(f"API响应类型: {type(result)}")
+            logger.debug(f"API响应键: {list(result.keys()) if isinstance(result, dict) else '非字典类型'}")
             
             return result
     
@@ -53,7 +56,7 @@ class ImageGenerationService:
             # 移除可能的空白字符
             base64_data = base64_data.strip()
             
-            print(f"[DEBUG] 开始解码base64数据，长度: {len(base64_data)}")
+            logger.debug(f"开始解码base64数据，长度: {len(base64_data)}")
             
             # 解码 base64 数据
             image_bytes = base64.b64decode(base64_data)
@@ -62,7 +65,7 @@ class ImageGenerationService:
             if len(image_bytes) == 0:
                 raise Exception("解码后的图像数据为空")
             
-            print(f"[DEBUG] 图像数据大小: {len(image_bytes)} bytes")
+            logger.debug(f"图像数据大小: {len(image_bytes)} bytes")
             
             # 确保目录存在
             image_dir = Path(settings.generated_images_dir)
@@ -73,13 +76,13 @@ class ImageGenerationService:
             with open(image_path, "wb") as f:
                 f.write(image_bytes)
             
-            print(f"[DEBUG] 图像已保存到: {image_path}")
+            logger.debug(f"图像已保存到: {image_path}")
             
             return str(image_path)
         except Exception as e:
-            print(f"[ERROR] 保存图像失败: {str(e)}")
-            print(f"[ERROR] base64数据长度: {len(base64_data) if base64_data else 0}")
-            print(f"[ERROR] base64数据前100字符: {base64_data[:100] if base64_data else 'None'}")
+            logger.error(f"保存图像失败: {str(e)}")
+            logger.error(f"base64数据长度: {len(base64_data) if base64_data else 0}")
+            logger.error(f"base64数据前100字符: {base64_data[:100] if base64_data else 'None'}")
             raise Exception(f"保存图像失败: {str(e)}")
     
     def generate_image_id(self) -> str: