feat: add comparison and user API endpoints

New API routes under src/app/api/ for comparisons and user operations.

src/app/api/comparisons/[slug]/route.ts

@@ -0,0 +1,24 @@
+import { db } from "@/lib/db";
+import { comparisons } from "@/lib/db/schema";
+import { eq, sql } from "drizzle-orm";
+import { getComparison } from "@/app/actions/comparison";
+
+export async function GET(
+  _request: Request,
+  { params }: { params: Promise<{ slug: string }> }
+) {
+  const { slug } = await params;
+
+  await db
+    .update(comparisons)
+    .set({ viewCount: sql`${comparisons.viewCount} + 1` })
+    .where(eq(comparisons.slug, slug));
+
+  const comparison = await getComparison(slug);
+
+  if (!comparison) {
+    return Response.json({ error: "Not found" }, { status: 404 });
+  }
+
+  return Response.json(comparison);
+}