web UI added and refactoring done

python_app/models/run_config_schema.py

@@ -21,9 +21,10 @@ class ComboModel:
 class RadarSweepModel:
     """Sweep settings for LibreVNA acquisition."""
 
-    # Keep schema defaults minimal/safe; operational values come from run_config.json.
-    start_hz: float = 0.0
-    stop_hz: float = 0.0
+    # A valid default range (stop > start) so a bare/default config is self-consistent;
+    # operational values come from run_config.json. (1 MHz .. 6 GHz mirrors the real configs.)
+    start_hz: float = 1_000_000.0
+    stop_hz: float = 6_000_000_000.0
     points: int = 1
     if_bandwidth_hz: float = 1.0
     power_dbm: float = -30.0