Update Hackathon PR Metrics Queries

- Change PR query to use `user_profile` instead of `user` for participant counting
- Modify merged PR query to use `is_merged=True` instead of `state="merged"`
- Refine hackathon detail view metrics calculation for more accurate PR tracking

Author: DonnieBLT

website/views/hackathon.py

@@ -114,7 +114,7 @@ def get_context_data(self, **kwargs):
                 created_at__lte=hackathon.end_time,
                 type="pull_request",
             )
-            .values("user")
+            .values("user_profile")
             .distinct()
             .count()
         )
@@ -137,7 +137,7 @@ def get_context_data(self, **kwargs):
             created_at__gte=hackathon.start_time,
             created_at__lte=hackathon.end_time,
             type="pull_request",
-            state="merged",
+            is_merged=True,
         ).count()
 
         context["merged_pr_count"] = merged_pr_count