fix(disputed): add admin role + contact info in discussion modal

- request-discussion endpoint: add 'admin' to allowed roles
- Return rejector_email and rejector_role in the response
- Modal success state shows contact card with username, role, email link
  so the approving lead can immediately reach out to the rejecting lead

backend/app/routers/tests.py

@@ -754,7 +754,7 @@ def sync_tempo(
 def request_discussion(
     test_id: uuid.UUID,
     db: Session = Depends(get_db),
-    current_user: User = Depends(require_any_role("red_lead", "blue_lead")),
+    current_user: User = Depends(require_any_role("red_lead", "blue_lead", "admin")),
 ):
     """Called when the approving lead confirms their vote in a disputed test.
 
@@ -774,12 +774,12 @@ def request_discussion(
     role = current_user.role
 
     # Identify who the "other lead" is (the one who rejected)
-    if role == "red_lead" and test.red_validation_status == "approved":
+    if (role in ("red_lead", "admin")) and test.red_validation_status == "approved":
         # Red approved, Blue rejected → notify Blue Lead who rejected
         rejector_id = test.blue_validated_by
         rejector_label = "Blue Lead"
         requester_label = "Red Lead"
-    elif role == "blue_lead" and test.blue_validation_status == "approved":
+    elif (role in ("blue_lead", "admin")) and test.blue_validation_status == "approved":
         # Blue approved, Red rejected → notify Red Lead who rejected
         rejector_id = test.red_validated_by
         rejector_label = "Red Lead"
@@ -787,15 +787,16 @@ def request_discussion(
     else:
         from app.domain.errors import BusinessRuleViolation
         raise BusinessRuleViolation(
-            "You are not the approving lead in this conflict or the state is inconsistent"
+            "The conflict state is inconsistent — no approving lead found"
         )
 
-    # Look up the rejecting lead's username for the message
+    # Look up the rejecting lead's full info for the response
     rejector = (
         db.query(UserModel).filter(UserModel.id == rejector_id).first()
         if rejector_id else None
     )
     rejector_name = rejector.username if rejector else rejector_label
+    rejector_email = getattr(rejector, "email", None) if rejector else None
 
     # Notify the rejecting lead
     if rejector_id:
@@ -833,6 +834,8 @@ def request_discussion(
         "status": "notification_sent",
         "message": f"Discussion request sent to {rejector_name}",
         "rejector_username": rejector_name,
+        "rejector_email": rejector_email,
+        "rejector_role": rejector_label,
     }