Fix span duplicates and metrics

Implements complete plan to resolve duplicate span_id issues and metric collection errors:
- Ensure edge handlers return proper Response objects to prevent double logging
- Update collect-metrics to use valid metric categories, fix system_alerts query, and adjust returns
- Apply detect-anomalies adjustments if needed and add defensive handling in wrapper
- Prepare ground for end-to-end verification of location-related fixes

supabase/functions/_shared/edgeFunctionWrapper.ts

@@ -266,7 +266,15 @@ export function wrapEdgeFunction(
       logSpanToDatabase(span, requestId);
 
       // Clone response to add tracking headers
-      const responseBody = await response.text();
+      // Defensive check: ensure handler returned a Response object
+      let responseBody: string;
+      if (response instanceof Response) {
+        responseBody = await response.text();
+      } else {
+        // Handler returned non-Response (shouldn't happen, but handle it)
+        addSpanEvent(span, 'warning_non_response_object');
+        responseBody = JSON.stringify(response);
+      }
       const enhancedResponse = new Response(responseBody, {
         status: response.status,
         statusText: response.statusText,