feat: public site homepage, search, and article reader

- Add editorial/magazine-style public layout with serif wordmark.
- Build homepage with three bias columns and editor's picks.
- Add search page with query, bias filter, and sort tabs.
- Add article detail page with summary, bias badge, and reasoning.
- Article cards include expandable "Why this classification?" panel.
- Style with warm, retro-editorial color palette and responsive layout.

src/app/api/articles/route.ts

@@ -0,0 +1,36 @@
+import { NextResponse } from 'next/server';
+import { prisma } from '@/lib/db';
+import { Bias } from '@prisma/client';
+
+export async function GET(request: Request) {
+  const { searchParams } = new URL(request.url);
+  const query = searchParams.get('q') || '';
+  const bias = searchParams.get('bias') as Bias | null;
+  const sort = searchParams.get('sort') || 'rank';
+  const limit = Number(searchParams.get('limit') || '50');
+  const offset = Number(searchParams.get('offset') || '0');
+
+  const orderBy = sort === 'date'
+    ? { publishedAt: 'desc' as const }
+    : { rankScore: 'desc' as const };
+
+  const articles = await prisma.article.findMany({
+    where: {
+      status: 'PUBLISHED',
+      ...(bias && { primaryBias: bias }),
+      ...(query && {
+        OR: [
+          { title: { contains: query } },
+          { summary: { contains: query } },
+          { topics: { contains: query } },
+        ],
+      }),
+    },
+    orderBy: [orderBy, { publishedAt: 'desc' }],
+    take: limit,
+    skip: offset,
+    include: { source: true },
+  });
+
+  return NextResponse.json({ articles });
+}