feat: add Card and Navbar components with styles

- Implemented Card component with cover, title, subtitle, content, and footer slots.
- Added styles for Card component in _card.scss.
- Created Navbar component with brand and links, including styles in _navbar.scss.
- Updated index.astro to include new Card and Navbar components.

src/components/Navbar/_navbar.scss

@@ -0,0 +1,55 @@
+@use "../../styles/tokens/typography" as *;
+
+.navbar {
+  display: flex;
+  align-items: center;
+  gap: var(--nds-spacing-lg);
+  height: 60px;
+  padding: 0 var(--nds-spacing-lg);
+  background-color: var(--nds-surface);
+  border-bottom: var(--nds-border-width-thin) solid var(--nds-border);
+
+  &__brand {
+    display: flex;
+    align-items: center;
+    gap: var(--nds-spacing-xs);
+  }
+  &__mark {
+    width: 24px;
+    height: 24px;
+    border-radius: var(--nds-radius-md);
+    background: linear-gradient(135deg, var(--nds-primary), var(--nds-accent));
+  }
+  &__title {
+    @include text-xl;
+    font-size: 1rem;
+    color: var(--nds-text);
+  }
+
+  &__links {
+    display: flex;
+    align-items: center;
+    gap: var(--nds-spacing-2xs);
+    flex: 1;
+  }
+  &__link {
+    padding: var(--nds-spacing-2xs) var(--nds-spacing-sm);
+    border-radius: var(--nds-radius-md);
+    @include text-label;
+    color: var(--nds-neutral);
+    text-decoration: none;
+    transition: all 120ms ease;
+    &:hover {
+      color: var(--nds-text);
+      background-color: var(--nds-surface-hover);
+    }
+    &--active {
+      color: var(--nds-text);
+    }
+  }
+  &__right {
+    display: flex;
+    align-items: center;
+    gap: var(--nds-spacing-sm);
+  }
+}

src/components/Navbar/navbar.astro

@@ -0,0 +1,19 @@
+---
+export interface Props {
+  brand?: string;
+}
+const { brand = "Nova" } = Astro.props;
+---
+
+<header class="navbar">
+  <div class="navbar__brand">
+    <span class="navbar__mark"></span>
+    <span class="navbar__title">{brand}</span>
+  </div>
+  <nav class="navbar__links"><slot /></nav>
+  <div class="navbar__right"><slot name="right" /></div>
+</header>
+
+<style lang="scss">
+  @use "./_navbar.scss";
+</style>