API notif dan penambahan package firebase-admin

Add:
- src/app/api/mobile/notifications/
- src/lib/firebase-admin.ts

### No Issue

src/app/api/mobile/notifications/route.ts

@@ -0,0 +1,44 @@
+// app/api/test/notifications/route.ts
+import { adminMessaging } from "@/lib/firebase-admin";
+import { NextRequest, NextResponse } from "next/server";
+
+export async function POST(request: NextRequest) {
+  try {
+    const { data } = await request.json();
+    const { fcmToken, title, body: notificationBody } = data;
+
+    console.log("Data Notifikasi >>", data);
+
+    if (!fcmToken || !title) {
+      return NextResponse.json(
+        { error: "Missing fcmToken or title" },
+        { status: 400 }
+      );
+    }
+
+    const message = {
+      token: fcmToken,
+      notification: {
+        title,
+        body: notificationBody || "",
+      },
+      data: {
+        sentAt: new Date().toISOString(), // ✅ Simpan metadata di data
+        // contoh: senderId, type, etc.
+      },
+    };
+
+    console.log("[MSG]", message);
+
+    const response = await adminMessaging.send(message);
+    console.log("✅ FCM sent:", response);
+
+    return NextResponse.json({ success: true, messageId: response });
+  } catch (error: any) {
+    console.error("❌ FCM error:", error);
+    return NextResponse.json(
+      { error: error.message || "Failed to send FCM" },
+      { status: 500 }
+    );
+  }
+}