Fix dark mode: use legible logo and lighter link colors

- Add dark mode logo (logo-dark.png) for better visibility on dark backgrounds
- Use CSS .dark class selector to switch logos based on theme
- Make link colors lighter in dark mode (#cccccc instead of #aaaaaa)

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

app.py

@@ -143,10 +143,10 @@ theme = gr.themes.Base(
     color_accent_soft='*neutral_200',
     color_accent_soft_dark='*neutral_800',
     link_text_color='#555555',
-    link_text_color_dark='#aaaaaa',
-    link_text_color_active_dark='#888888',
-    link_text_color_hover_dark='#999999',
-    link_text_color_visited_dark='#888888',
+    link_text_color_dark='#cccccc',
+    link_text_color_active_dark='#bbbbbb',
+    link_text_color_hover_dark='#dddddd',
+    link_text_color_visited_dark='#bbbbbb',
     table_even_background_fill='*neutral_100',
     table_even_background_fill_dark='*neutral_800',
     button_primary_background_fill='*secondary_900',
@@ -180,6 +180,18 @@ except FileNotFoundError:
     logger.warning(f"Home icon file not found at {LOGO_PATH}")
     home_icon_data_uri = "none"
 
+# Load dark mode logo (PNG)
+LOGO_DARK_PATH = "assets/logo-dark.png"
+try:
+    import base64
+    with open(LOGO_DARK_PATH, "rb") as f:
+        dark_logo_content = f.read()
+    encoded_dark_logo = base64.b64encode(dark_logo_content).decode('utf-8')
+    home_icon_dark_data_uri = f"data:image/png;base64,{encoded_dark_logo}"
+except FileNotFoundError:
+    logger.warning(f"Dark mode logo file not found at {LOGO_DARK_PATH}")
+    home_icon_dark_data_uri = home_icon_data_uri  # Fallback to light logo
+
 # --- This is the final CSS ---
 final_css = css + f"""
 /* --- Find the "Home" button and replace its text with an icon --- */
@@ -198,7 +210,7 @@ final_css = css + f"""
     font-size: 0 !important;
     text-indent: -9999px;
 
-    /* 3. Apply the icon as the background */
+    /* 3. Apply the icon as the background (light mode) */
     background-image: url("{home_icon_data_uri}") !important;
     background-size: contain !important;
     background-repeat: no-repeat !important;
@@ -210,6 +222,11 @@ final_css = css + f"""
     border: none !important;
     outline: none !important;
 }}
+
+/* Dark mode logo override */
+.dark .nav-holder nav a[href*="/home"] {{
+    background-image: url("{home_icon_dark_data_uri}") !important;
+}}
 """
 # --- Gradio App Definition ---
 logger.info("Creating Gradio application")