Refactor statistics page and enhance logging

- Updated the layout and styling of the statistics page for better responsiveness and visual appeal.
- Introduced a new error page for 404 errors with user-friendly messaging and navigation options.
- Enhanced logging functionality to capture detailed events related to asset uploads, deletions, and HTTP requests.
- Implemented an AssetTracker to manage assets in memory, allowing for efficient tracking and retrieval.
- Improved the API for uploading and retrieving assets, ensuring better error handling and response formatting.
- Added auto-refresh functionality to the statistics page to keep data up-to-date.

README.md

@@ -88,7 +88,6 @@ GET /api/stats
   "storage_bytes": 1048576,
   "image_count": 3,
   "text_count": 2,
-  "avg_response_ms": 0.85,
   "total_requests": 150,
   "recent_activity": [...]
 }