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/static/favicon.svg

@@ -0,0 +1,11 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32">
+  <rect width="32" height="32" rx="6" fill="#1B365D"/>
+  <g fill="none" stroke="#f5f4ed" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M8 7h6a2 2 0 0 1 2 2v16l-1-1-2 1-2-1-2 1V9a1 1 0 0 1 1-1z"/>
+    <path d="M24 7h-6a2 2 0 0 0-2 2v16l1-1 2 1 2-1 2 1V9a1 1 0 0 0-1-1z"/>
+    <line x1="12" y1="12" x2="12" y2="12.01"/>
+    <line x1="12" y1="16" x2="12" y2="16.01"/>
+    <line x1="20" y1="12" x2="20" y2="12.01"/>
+    <line x1="20" y1="16" x2="20" y2="16.01"/>
+  </g>
+</svg>