fix web page issues

hbd/server/threshold.py

@@ -114,11 +114,19 @@ class AlertState:
     
     def to_dict(self) -> dict:
         """Convert alert state to dictionary for serialization."""
+        import math
+        
+        # Helper to sanitize numeric values for JSON (handle inf/nan)
+        def sanitize_value(val):
+            if isinstance(val, float) and (math.isinf(val) or math.isnan(val)):
+                return None
+            return val
+        
         result = {
             "metric_path": self.metric_path,
             "level": self.level.name,
             "since": self.since,
-            "last_value": self.last_value,
+            "last_value": sanitize_value(self.last_value),
             "last_check": self.last_check,
             "notification_count": self.notification_count,
             "acknowledged": self.acknowledged,
@@ -130,7 +138,7 @@ class AlertState:
         
         # Include threshold info if available
         if self.threshold_value is not None:
-            result["threshold_value"] = self.threshold_value
+            result["threshold_value"] = sanitize_value(self.threshold_value)
         if self.operator is not None:
             result["operator"] = self.operator
         if self.formatted_message is not None: