feat: implement AI-driven METAR summary service and dashboard UI components

frontend/app/api/ai/metar-summary/route.ts

@@ -0,0 +1,69 @@
+import { NextRequest, NextResponse } from "next/server";
+import {
+  applyAuthResponseCookies,
+  buildBackendRequestHeaders,
+} from "@/lib/backend-auth";
+
+const API_BASE = process.env.POLYWEATHER_API_BASE_URL;
+
+export const dynamic = "force-dynamic";
+export const maxDuration = 30;
+
+export async function POST(req: NextRequest) {
+  if (!API_BASE) {
+    return NextResponse.json(
+      { error: "POLYWEATHER_API_BASE_URL is not configured" },
+      { status: 500 },
+    );
+  }
+
+  let body: unknown = {};
+  try {
+    body = await req.json();
+  } catch {
+    body = {};
+  }
+
+  const requestBody =
+    body && typeof body === "object" ? (body as Record<string, unknown>) : {};
+  const auth = await buildBackendRequestHeaders(req);
+  const headers = new Headers(auth.headers);
+  headers.set("Content-Type", "application/json");
+  headers.set("Accept", "text/event-stream");
+
+  try {
+    const res = await fetch(`${API_BASE}/api/ai/metar-summary`, {
+      method: "POST",
+      headers,
+      cache: "no-store",
+      body: JSON.stringify(requestBody),
+    });
+    if (!res.ok || !res.body) {
+      const raw = await res.text();
+      const response = NextResponse.json(
+        { error: `Backend returned ${res.status}`, detail: raw.slice(0, 300) },
+        { status: res.status === 402 || res.status === 403 ? res.status : 502 },
+      );
+      return applyAuthResponseCookies(response, auth.response);
+    }
+
+    const response = new NextResponse(res.body, {
+      status: 200,
+      headers: {
+        "Content-Type": "text/event-stream; charset=utf-8",
+        "Cache-Control": "no-store, no-transform",
+        "X-Accel-Buffering": "no",
+      },
+    });
+    return applyAuthResponseCookies(response, auth.response);
+  } catch (error) {
+    const response = NextResponse.json(
+      {
+        error: "Failed to stream METAR summary",
+        detail: String(error),
+      },
+      { status: 500 },
+    );
+    return applyAuthResponseCookies(response, auth.response);
+  }
+}