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/utils.py

@@ -19,7 +19,17 @@ TMP_DIR = DATA_DIR / "tmp"
 
 # ── 模板单例 ──────────────────────────────────────────────────────────
 
-templates = Jinja2Templates(directory="app/templates")
+
+class _Templates(Jinja2Templates):
+    """自动注入 is_admin 到模板上下文的 Jinja2Templates 子类。"""
+
+    def TemplateResponse(self, request, name, context=None, **kwargs):
+        context = context or {}
+        context.setdefault("is_admin", request.session.get("is_admin", False))
+        return super().TemplateResponse(request, name, context, **kwargs)
+
+
+templates = _Templates(directory="app/templates")
 
 
 # ── 时区工具 ──────────────────────────────────────────────────────────