feat: add notifications view and update branding

- Add complete notifications management view with:
  - Service status display (Discord, Telegram)
  - Test notification functionality
  - Service management (delete/disable)
  - Filter settings display (case sensitive/insensitive)
- Update API types to match current backend structure
- Fix NotificationFilters type (remove deprecated fields)
- Update page title from 'Vite + React + TS' to 'Leggen'
- Replace Vite favicon with custom Leggen favicon
- Add notifications tab to main navigation
- Ensure full API compatibility with current backend

frontend/src/lib/utils.ts

@@ -13,9 +13,9 @@ export function formatCurrency(amount: number, currency: string = 'EUR'): string
       style: 'currency',
       currency: validCurrency,
     }).format(amount);
-  } catch (error) {
-    // Fallback if currency is still invalid
-    console.warn(`Invalid currency code: ${currency}, falling back to EUR`);
+   } catch {
+     // Fallback if currency is still invalid
+     console.warn(`Invalid currency code: ${currency}, falling back to EUR`);
     return new Intl.NumberFormat('en-US', {
       style: 'currency',
       currency: 'EUR',