docs: cache-bust demo screenshots with ?v=2

GitHub's camo image proxy keys its cache on the URL, so replacing the
file in place kept serving the old screenshots in README.md.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: hyglgithub

README.md

@@ -28,11 +28,11 @@
 
 ## 功能演示
 
-![字幕抓取功能](docs/screenshots/demo-subtitle.png)
+![字幕抓取功能](docs/screenshots/demo-subtitle.png?v=2)
 
 <br>
 
-![文档整理功能](docs/screenshots/demo-doc-organize.png)
+![文档整理功能](docs/screenshots/demo-doc-organize.png?v=2)
 
 ## 使用教程
 

docs/index.html

@@ -483,13 +483,13 @@ <h1 class="hero-title">
               <div class="slide-content">
                 <h3 class="slide-title">抓取字幕 & 智能截图</h3>
               </div>
-              <img src="screenshots/demo-subtitle.png" alt="字幕抓取演示" class="slide-img">
+              <img src="screenshots/demo-subtitle.png?v=2" alt="字幕抓取演示" class="slide-img">
             </div>
             <div class="carousel-slide">
               <div class="slide-content">
                 <h3 class="slide-title">自动整理</h3>
               </div>
-              <img src="screenshots/demo-doc-organize.png" alt="AI文档整理演示" class="slide-img">
+              <img src="screenshots/demo-doc-organize.png?v=2" alt="AI文档整理演示" class="slide-img">
             </div>
           </div>
           <span class="dot active" onclick="goToSlide(0)"></span>