Add static preview image for Open Graph social sharing

- Resized to 1200x735 and converted to JPEG for smaller file size (52KB)

Co-authored-by: openhands <openhands@all-hands.dev>

app.py

@@ -40,17 +40,16 @@ logger.info(f"All modules imported (LOCAL_DEBUG={LOCAL_DEBUG})")
 api = HfApi()
 LOGO_PATH = "assets/logo.svg"
 # Open Graph / Social Media Preview Meta Tags
-# Using the OpenHands logo served via Gradio's file endpoint
 og_meta_tags = """
 <meta property="og:title" content="OpenHands Index" />
 <meta property="og:description" content="A Holistic Benchmark for Software Engineering" />
-<meta property="og:image" content="https://index.openhands.dev/file/assets/openhands_logo_color_forwhite.png" />
+<meta property="og:image" content="https://index.openhands.dev/file/assets/openhands-index-preview.jpg" />
 <meta property="og:url" content="https://index.openhands.dev" />
 <meta property="og:type" content="website" />
 <meta name="twitter:card" content="summary_large_image" />
 <meta name="twitter:title" content="OpenHands Index" />
 <meta name="twitter:description" content="A Holistic Benchmark for Software Engineering" />
-<meta name="twitter:image" content="https://index.openhands.dev/file/assets/openhands_logo_color_forwhite.png" />
+<meta name="twitter:image" content="https://index.openhands.dev/file/assets/openhands-index-preview.jpg" />
 """
 
 # JavaScripts