Fix RECOVER routing: use consistent level name and route via alerted channel

threshold.py was emitting level="RECOVERED" for metric recoveries, which
failed the is_recover check in send_notification (which only matched "RECOVER"),
bypassing _alerted_channels routing and the min_level bypass added in the
previous commit. Changed to "RECOVER" so all recovery paths are consistent.

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

hbd/server/threshold.py

@@ -948,7 +948,7 @@ class ThresholdChecker:
 
         # Format message
         if new_level == AlertLevel.OK:
-            lvl = "RECOVERED"
+            lvl = "RECOVER"
             message = f"{metric_path} = {display_value} ({old_level.name} -> OK)"
         elif new_level == AlertLevel.WARNING:
             lvl = "WARNING"