feat: enhance UI, refactor services, improve templates and tests

- Replace image_extractor with pdf_image_extractor service
- Enhance pi_client with expanded API capabilities
- Improve summarizer service with additional features
- Update admin routes with more endpoints
- Add login page template
- Enhance detail page with comprehensive layout
- Improve search and trends pages
- Update base template with additional elements
- Refactor tests for better coverage
- Add validate_summary script
- Update project configuration and dependencies

app/config.py

@@ -16,7 +16,9 @@ class Settings(BaseSettings):
     APP_TIMEZONE: str = "Asia/Shanghai"
 
     # 安全
-    ADMIN_TOKEN: str = "change-me"
+    ADMIN_USERNAME: str = "admin"
+    ADMIN_PASSWORD: str = ""
+    SECRET_KEY: str = "change-me"
 
     # HuggingFace / arXiv
     HF_API_BASE: str = "https://huggingface.co/api"