feat: implement Navbar styling with responsive design and add localStorage mock to Navbar tests.

src/components/layout/Navbar.module.css

@@ -172,7 +172,7 @@
     flex-direction: column;
     gap: 0;
     padding: var(--space-lg);
-    background-color: rgba(15, 20, 16, 0.98);
+    background-color: rgba(15, 20, 16, 0.85);
     backdrop-filter: blur(12px);
     border-bottom: 1px solid var(--md-sys-color-outline-variant);
     transform: translateY(-100%);

src/components/layout/Navbar.test.tsx

@@ -16,6 +16,18 @@ describe('Navbar Performance', () => {
       configurable: true,
       get: scrollYGetterSpy as any,
     });
+
+    // Mock localStorage
+    Object.defineProperty(window, 'localStorage', {
+      value: {
+        getItem: vi.fn(),
+        setItem: vi.fn(),
+        removeItem: vi.fn(),
+        clear: vi.fn(),
+      },
+      writable: true,
+    });
+
     vi.useFakeTimers();
   });