Add comprehensive backend features and mobile UI improvements

Backend:
- Add 2FA authentication with TOTP support
- Add API keys management system
- Add audit logging for security events
- Add file upload/management system
- Add notifications system with preferences
- Add session management
- Add webhooks integration
- Add analytics endpoints
- Add export functionality
- Add password policy enforcement
- Add new database migrations for core tables

Frontend:
- Add module position system (top/bottom sidebar sections)
- Add search and notifications module configuration tabs
- Add mobile logo replacing hamburger menu
- Center page title absolutely when no tabs present
- Align sidebar footer toggles with navigation items
- Add lighter icon color in dark theme for mobile
- Add API keys management page
- Add notifications page with context
- Add admin analytics and audit logs pages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/styles/theme/index.css

@@ -46,6 +46,12 @@ body {
   cursor: text;
 }
 
+/* Utility for monospace text (IDs, keys, timestamps) */
+.mono {
+  font-family: var(--font-mono);
+  font-variant-numeric: tabular-nums;
+}
+
 #root {
   min-height: 100vh;
   width: 100%;