feat: Auto-update TLE data on app startup

- Add refresh_tle_data() function for reusable TLE updates
- Automatically fetch fresh TLE from CelesTrak when app starts
- Runs in background thread to avoid slowing down startup
- Includes NOAA-20 and NOAA-21 in name mappings
- Gracefully handles failures (uses cached data if offline)
- Existing /update-tle endpoint now uses shared function

This ensures satellite tracking data is always fresh, fixing
inaccurate positions caused by stale TLE data.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app.py

@@ -714,6 +714,22 @@ def main() -> None:
     from routes import register_blueprints
     register_blueprints(app)
 
+    # Update TLE data in background thread (non-blocking)
+    def update_tle_background():
+        try:
+            from routes.satellite import refresh_tle_data
+            print("Updating satellite TLE data from CelesTrak...")
+            updated = refresh_tle_data()
+            if updated:
+                print(f"TLE data updated for: {', '.join(updated)}")
+            else:
+                print("TLE update: No satellites updated (may be offline)")
+        except Exception as e:
+            print(f"TLE update failed (will use cached data): {e}")
+
+    tle_thread = threading.Thread(target=update_tle_background, daemon=True)
+    tle_thread.start()
+
     # Initialize WebSocket for audio streaming
     try:
         from routes.audio_websocket import init_audio_websocket