Add portfolio template to combined marketing+portfolio template

- Added portfolio pages: portfolio-index, portfolio-about, portfolio-contact
- Added work/[slug].astro for project detail pages
- Added PortfolioBase.astro layout with Playfair Display font
- Added ProjectCard.astro component
- Added projects collection with taxonomies (category, tag)
- Updated theme.css with --font-serif variable
- Added portfolio seed data with 4 projects
- Updated menus to include Work link

src/pages/portfolio-about.astro

@@ -0,0 +1,65 @@
+---
+import { getEmDashEntry } from "emdash";
+import PortfolioBase from "../layouts/PortfolioBase.astro";
+
+const { entry: page, cacheHint } = await getEmDashEntry("pages", "about");
+Astro.cache.set(cacheHint);
+---
+
+<PortfolioBase title="About">
+	<main class="container">
+		<article>
+			<h1>About Us</h1>
+			{page?.data?.content ? (
+				<div class="content">
+					{page.data.content.map((block: any) => {
+						if (block._type === "block") {
+							return <p>{block.children?.map((c: any) => c.text).join("")}</p>;
+						}
+						return null;
+					})}
+				</div>
+			) : (
+				<div class="content">
+					<p>We are a creative studio focused on design and development.</p>
+					<p>Add your about page content in the admin panel.</p>
+					<a href="/_emdash/admin">Open Admin</a>
+				</div>
+			)}
+		</article>
+	</main>
+</PortfolioBase>
+
+<style>
+	main.container {
+		padding: var(--spacing-5xl) var(--spacing-lg);
+		max-width: 800px;
+		margin: 0 auto;
+	}
+
+	article h1 {
+		font-size: var(--font-size-4xl);
+		margin-bottom: var(--spacing-2xl);
+		font-family: var(--font-serif);
+	}
+
+	.content {
+		font-size: var(--font-size-lg);
+		line-height: 1.7;
+	}
+
+	.content p {
+		margin-bottom: var(--spacing-lg);
+	}
+
+	.content a {
+		display: inline-block;
+		margin-top: var(--spacing-lg);
+		padding: var(--spacing-md) var(--spacing-xl);
+		background: var(--color-primary);
+		color: white;
+		text-decoration: none;
+		border-radius: var(--radius);
+		font-weight: 600;
+	}
+</style>