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

.env.example

@@ -1,12 +1,14 @@
 # ─── 应用 ────────────────────────────────
-APP_HOST=0.0.0.0
+APP_HOST=127.0.0.1
 APP_PORT=8000
 APP_DEBUG=false
 BASE_URL=http://127.0.0.1:8000
 APP_TIMEZONE=Asia/Shanghai
 
 # ─── 安全 ────────────────────────────────
-ADMIN_TOKEN=your_admin_token_here
+ADMIN_USERNAME=admin
+ADMIN_PASSWORD=your_secure_password
+SECRET_KEY=your_random_secret_key
 
 # ─── HuggingFace / arXiv ────────────────
 HF_API_BASE=https://huggingface.co/api
@@ -19,7 +21,7 @@ HTTP_USER_AGENT=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
 # ─── AI 总结 ──────────────────────────────
 PI_BIN=
 SUMMARY_SKILL=daily-paper-summary
-SUMMARY_CONCURRENCY=2
+SUMMARY_CONCURRENCY=3
 SUMMARY_TIMEOUT_SECONDS=300
 SUMMARY_MAX_RETRIES=1