feat: add solutions list/detail pages

- types: SolutionPageSummary/Detail
- services/solution.service.ts
- app/solutions: list + detail pages
- Header nav: add 解决方案 link

app/solutions/[slug]/page.tsx

@@ -0,0 +1,39 @@
+import { notFound } from "next/navigation";
+import type { Metadata } from "next";
+import { getSolutionBySlug } from "@/services/solution.service";
+import { BlockRenderer } from "@/blocks/BlockRenderer";
+
+interface SolutionDetailPageProps {
+  params: Promise<{ slug: string }>;
+}
+
+export async function generateMetadata({
+  params,
+}: SolutionDetailPageProps): Promise<Metadata> {
+  const { slug } = await params;
+  const solution = await getSolutionBySlug(slug).catch(() => null);
+  return { title: solution?.title ?? "解决方案未找到" };
+}
+
+export default async function SolutionDetailPage({
+  params,
+}: SolutionDetailPageProps) {
+  const { slug } = await params;
+  const solution = await getSolutionBySlug(slug).catch(() => null);
+
+  if (!solution) {
+    notFound();
+  }
+
+  return (
+    <article className="mx-auto max-w-3xl px-6 py-24">
+      <h1 className="mb-2 text-4xl font-bold text-slate-900">
+        {solution.title}
+      </h1>
+      {solution.industry && (
+        <p className="mb-12 text-sm text-slate-500">{solution.industry}</p>
+      )}
+      <BlockRenderer blocks={solution.body} />
+    </article>
+  );
+}