feat: 实现联系表单提交与邮件通知功能

添加联系表单提交接口和邮件通知功能，支持从环境变量读取 SMTP 配置
重构 SEO 配置到 site.json，新增 robots.txt 和 sitemap.xml 生成
更新公司电话并添加 PM2 生产运行配置

app/api/contact/route.ts

@@ -0,0 +1,79 @@
+import { NextResponse } from "next/server"
+import { ZodError } from "zod"
+import { contactFormSchema } from "@/lib/contact-form"
+import { sendContactNotification } from "@/lib/contact-mailer"
+import { ContactMailerConfigError, loadContactMailerConfig } from "@/lib/contact-mailer-config"
+
+export const runtime = "nodejs"
+
+function getClientIp(request: Request) {
+  const forwardedFor = request.headers.get("x-forwarded-for")
+
+  if (forwardedFor) {
+    return forwardedFor.split(",")[0]?.trim() || "unknown"
+  }
+
+  return request.headers.get("x-real-ip") ?? "unknown"
+}
+
+function formatSubmittedAt() {
+  return new Intl.DateTimeFormat("zh-CN", {
+    timeZone: "Asia/Shanghai",
+    dateStyle: "full",
+    timeStyle: "long",
+  }).format(new Date())
+}
+
+export async function POST(request: Request) {
+  let requestBody: unknown
+
+  try {
+    requestBody = await request.json()
+  } catch {
+    return NextResponse.json(
+      { error: "请求格式不正确，请刷新后重试。" },
+      { status: 400 }
+    )
+  }
+
+  try {
+    const payload = contactFormSchema.parse(requestBody)
+    const config = await loadContactMailerConfig()
+
+    await sendContactNotification({
+      config,
+      payload,
+      meta: {
+        submittedAt: formatSubmittedAt(),
+        sourceUrl: request.headers.get("referer") ?? request.headers.get("origin") ?? new URL(request.url).origin,
+        ipAddress: getClientIp(request),
+        userAgent: request.headers.get("user-agent") ?? "unknown",
+      },
+    })
+
+    return NextResponse.json({ ok: true })
+  } catch (error) {
+    if (error instanceof ZodError) {
+      return NextResponse.json(
+        { error: error.issues[0]?.message ?? "提交信息不完整，请检查后重试。" },
+        { status: 400 }
+      )
+    }
+
+    if (error instanceof ContactMailerConfigError) {
+      console.error(error.message)
+
+      return NextResponse.json(
+        { error: "邮件通知配置不完整，请联系管理员检查 SMTP 设置。" },
+        { status: 500 }
+      )
+    }
+
+    console.error("Failed to send contact notification", error)
+
+    return NextResponse.json(
+      { error: "提交失败，邮件通知未发送成功，请稍后重试。" },
+      { status: 500 }
+    )
+  }
+}