Optimize forecast frequency: every 3 hours for first 2 days

- First 48 hours: Every 3 hours (0,3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48)
- Days 3-4: Every 24 hours (72,96)
- Provides high accuracy for short-range forecasts
- Maintains 4-day coverage with efficient longer-range intervals
- Perfect for production weather apps requiring detailed near-term forecasts

🤖 Generated with [Claude Code](https://claude.ai/code)

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

app.py

@@ -290,8 +290,8 @@ def fetch_dwd_icon_data(lat, lon):
         nearest_idx = find_nearest_grid_point(lat, lon, grid_lats, grid_lons)
         print(f"Nearest grid point: {grid_lats[nearest_idx]:.3f}°N, {grid_lons[nearest_idx]:.3f}°E")
         
-        # Download and process forecast data for multiple hours
-        forecast_hours = [0, 3, 6, 12, 18, 24, 36, 48, 72, 96]  # Selected forecast hours
+        # Download and process forecast data - high frequency for first 2 days, then longer intervals  
+        forecast_hours = [0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 72, 96]  # Every 3hrs for 48hrs, then 24hr intervals
         weather_data = {'times': [], 'data': {param: [] for param in parameters.keys()}}
         
         for fh in forecast_hours: