fix(tests): pause reopen timer, lock edits to assignee, restore Jira operator on reopen

- reopen_red_review starts the timer paused (paused_at set) instead of
  immediately running, since the operator hasn't resumed working yet —
  blue already did this via blue_work_started_at, red needed the same
  behavior via the existing pause/resume mechanism.
- update_test_red/update_test_blue now lock edits to the actual assigned
  operator for leads too, not just techs — a lead could previously edit
  another operator's in-progress test. Mirrored in TeamTabs.tsx.
- push_test_event reassigns the Jira ticket to the original operator
  (not the reopening lead) when a test returns to red_executing or
  blue_evaluating for rework, instead of leaving it on the lead.

backend/app/routers/tests.py

@@ -672,11 +672,13 @@ def update_test_red(
     Returns:
         TestOut: The updated test with refreshed red-team field values.
     """
-    # Assignee lock: red_tech cannot work a test assigned to someone else
+    # Assignee lock: only the operator actually assigned to this test may
+    # edit it — applies to red_lead too, not just red_tech, since a lead
+    # editing another operator's in-progress test is exactly as wrong as
+    # a different tech doing it.
     _pre_test = crud_get_test_or_raise(db, test_id)
     if (
         _pre_test.red_tech_assignee is not None
-        and current_user.role == "red_tech"
         and _pre_test.red_tech_assignee != current_user.id
     ):
         raise HTTPException(status_code=403, detail="Test is assigned to another operator")
@@ -738,11 +740,11 @@ def update_test_blue(
     Returns:
         TestOut: The updated test with refreshed blue-team field values.
     """
-    # Assignee lock: blue_tech cannot work a test assigned to someone else
+    # Assignee lock: only the operator actually assigned to this test may
+    # edit it — applies to blue_lead too, not just blue_tech.
     _pre_test = crud_get_test_or_raise(db, test_id)
     if (
         _pre_test.blue_tech_assignee is not None
-        and current_user.role == "blue_tech"
         and _pre_test.blue_tech_assignee != current_user.id
     ):
         raise HTTPException(status_code=403, detail="Test is assigned to another operator")