Add secret management guide, client-side performance monitoring, and search accessibility enhancements

- Introduced a comprehensive Secret Management Guide detailing best practices, secret classification, development setup, production management, rotation procedures, and emergency protocols.
- Implemented a client-side performance monitoring script to track various metrics including page load performance, paint metrics, layout shifts, and memory usage.
- Enhanced search accessibility with keyboard navigation support for search results, ensuring compliance with WCAG standards and improving user experience.

.gitignore

@@ -34,6 +34,12 @@ db.sqlite3-journal
 .uv/
 backend/.uv/
 
+# Generated requirements files (auto-generated from pyproject.toml)
+# Uncomment if you want to track these files
+# backend/requirements.txt
+# backend/requirements-dev.txt
+# backend/requirements-test.txt
+
 # Node.js
 node_modules/
 npm-debug.log*
@@ -98,8 +104,11 @@ temp/
 
 # Backup files
 *.bak
+*.backup
 *.orig
 *.swp
+*_backup.*
+*_OLD_*
 
 # Archive files
 *.tar.gz