Fix invisible CelesTrak dropdown options on Windows

Select option elements inherited white text color but rendered against
the system's default white dropdown background, making all entries
invisible. Explicit dark background on option elements fixes it.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: planet.jeroen

packages/pro/src/humeris/adapters/cesium_viewer.py

@@ -356,6 +356,7 @@ def generate_interactive_html(
             flex: 1; background: rgba(255,255,255,0.1); border: 1px solid rgba(255,255,255,0.2);
             color: #fff; padding: 3px 6px; border-radius: 3px; font-size: 11px;
         }}
+        .form-row select option {{ background: #222; color: #fff; }}
         .btn {{
             display: inline-block; padding: 4px 10px; margin: 2px;
             background: rgba(80,160,255,0.3); color: #fff;