fix(jira,tests): send real datetime to RT/BT date fields, resolve assignee usernames for operators

- RT/BT Start/End Date are genuine Jira "datetime" custom fields (confirmed
  via issue_editmeta), not plain dates. Pushing a bare "YYYY-MM-DD" string
  made Jira default the time-of-day to midnight, so RT Start Date and RT
  End Date ended up showing the same meaningless midnight timestamp instead
  of the actual execution window. Now sends a full ISO datetime.
- The test detail page showed "RT: Unassigned" for the operator who WAS
  correctly assigned, because GET /users/operators (the only source
  AssigneeControl used to resolve an assignee ID into a username) is
  restricted to leads/managers — a plain operator has no other way to
  resolve their own ID. TestOut now resolves and includes the assignee's
  username directly (red/blue tech + reviewer), so the badge no longer
  depends on a permission-gated list the viewer might not have access to.

backend/app/services/jira_service.py

@@ -1202,6 +1202,20 @@ def _select_field(value: str) -> dict:
     return {"value": value}
 
 
+def _jira_datetime(dt: datetime) -> str:
+    """Format a naive-UTC datetime for a Jira ``datetime``-type custom field.
+
+    RT/BT Start/End Date are genuine Jira datetime fields (confirmed via
+    issue_editmeta — schema type "datetime"), not plain dates. Sending a
+    bare "YYYY-MM-DD" string makes Jira default the time-of-day to
+    midnight, so RT Start Date and RT End Date ended up showing the same
+    meaningless midnight timestamp regardless of when the operator
+    actually started/finished. Jira's REST API expects
+    ``yyyy-MM-dd'T'HH:mm:ss.SSSZ`` for this field type.
+    """
+    return dt.strftime("%Y-%m-%dT%H:%M:%S.000+0000")
+
+
 def _compute_hours(start: Optional[datetime], end: Optional[datetime]) -> Optional[float]:
     """Return the elapsed time between two timestamps in hours, or None if unavailable."""
     if not start or not end:
@@ -1272,10 +1286,10 @@ def push_rt_submitted(db: Session, test: Test) -> None:
         else test.execution_start_time
     )
     if first_start:
-        fields[JIRA_FIELD_RT_START_DATE] = first_start.strftime("%Y-%m-%d")
+        fields[JIRA_FIELD_RT_START_DATE] = _jira_datetime(first_start)
 
     if test.execution_end_time:
-        fields[JIRA_FIELD_RT_END_DATE] = test.execution_end_time.strftime("%Y-%m-%d")
+        fields[JIRA_FIELD_RT_END_DATE] = _jira_datetime(test.execution_end_time)
 
     attack_success = _enum_value(test.attack_success)
     if attack_success in _ATTACK_SUCCESS_TO_JIRA:
@@ -1287,13 +1301,13 @@ def push_rt_submitted(db: Session, test: Test) -> None:
 def push_bt_started(db: Session, test: Test) -> None:
     """Set the BT Start Date field — called when Blue picks up the test to evaluate."""
     _update_test_fields(db, test, {
-        JIRA_FIELD_BT_START_DATE: datetime.utcnow().strftime("%Y-%m-%d"),
+        JIRA_FIELD_BT_START_DATE: _jira_datetime(datetime.utcnow()),
     })
 
 
 def push_bt_submitted(db: Session, test: Test) -> None:
     """Set BT End Date, Attack Detected/Contained, and time-to-detect/contain — Blue submits for review."""
-    fields: dict = {JIRA_FIELD_BT_END_DATE: datetime.utcnow().strftime("%Y-%m-%d")}
+    fields: dict = {JIRA_FIELD_BT_END_DATE: _jira_datetime(datetime.utcnow())}
 
     detection_result = _enum_value(test.detection_result)
     if detection_result in _DETECTION_TO_JIRA: