feat: use iframe to embed Step-Audio 2 project page

- Replace external link with iframe embedding
- Display StepFun official page directly in the project page
- Add responsive iframe container with proper aspect ratio
- Keep project summary and link below iframe

Author: FlyTia

content/projects/step-audio-2/index.md

@@ -1,7 +1,6 @@
 ---
 title: Step-Audio 2
 date: 2025-07-23
-external_link: https://www.stepfun.com/research/en/step-audio2
 tags:
   - Audio LLM
   - Speech Understanding
@@ -10,13 +9,26 @@ tags:
 summary: End-to-end multimodal large language model with audio reasoning capabilities, achieving SOTA performance on multiple benchmarks.
 ---
 
+<div style="position: relative; width: 100%; padding-bottom: 75%; overflow: hidden;">
+  <iframe 
+    src="https://www.stepfun.com/research/en/step-audio2" 
+    style="position: absolute; top: 0; left: 0; width: 100%; height: 100%; border: none;"
+    allowfullscreen
+    loading="lazy">
+  </iframe>
+</div>
+
+---
+
+**项目简介：**
+
 Step-Audio 2 is an end-to-end multimodal large language model engineered for industrial applications. This model innovatively integrates a latent space audio encoder with audio reinforcement learning.
 
-**Key Features:**
+**关键特性：**
 - Genuine end-to-end architecture eliminating traditional ASR+LLM+TTS pipelines
 - CoT-reinforcement learning fusion enabling audio reasoning capabilities
 - Acoustic knowledge enhancement via web search and audio retrieval
 - SOTA performance on MMAU, URO-Bench, and multiple ASR benchmarks
 
-[View Full Project →](https://www.stepfun.com/research/en/step-audio2)
+[访问完整页面 →](https://www.stepfun.com/research/en/step-audio2)