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/tests/test_jira_service.py

@@ -397,8 +397,8 @@ def test_push_rt_submitted_uses_execution_times_not_click_time(mock_get_client,
     jira_service.push_rt_submitted(db, test)
 
     fields = mock_jira.update_issue_field.call_args[1]["fields"]
-    assert fields[jira_service.JIRA_FIELD_RT_START_DATE] == "2026-03-01"
-    assert fields[jira_service.JIRA_FIELD_RT_END_DATE] == "2026-03-01"
+    assert fields[jira_service.JIRA_FIELD_RT_START_DATE] == "2026-03-01T09:00:00.000+0000"
+    assert fields[jira_service.JIRA_FIELD_RT_END_DATE] == "2026-03-01T11:00:00.000+0000"
 
 
 @patch("app.services.jira_service.has_admin_jira_configured", return_value=True)
@@ -439,8 +439,8 @@ def test_push_rt_submitted_rt_start_date_survives_reopen(mock_get_client, mock_c
     jira_service.push_rt_submitted(db, test)
 
     fields = mock_jira.update_issue_field.call_args[1]["fields"]
-    assert fields[jira_service.JIRA_FIELD_RT_START_DATE] == "2026-03-01"
-    assert fields[jira_service.JIRA_FIELD_RT_END_DATE] == "2026-03-05"
+    assert fields[jira_service.JIRA_FIELD_RT_START_DATE] == "2026-03-01T09:00:00.000+0000"
+    assert fields[jira_service.JIRA_FIELD_RT_END_DATE] == "2026-03-05T10:00:00.000+0000"
 
 
 @patch("app.services.jira_service.has_admin_jira_configured", return_value=True)

backend/tests/test_test_assignee_username.py

@@ -0,0 +1,63 @@
+"""GET /tests/{id} must resolve assignee IDs into usernames directly, since
+GET /users/operators (the only other source of that mapping) is restricted
+to leads/managers — a plain operator viewing their own assigned test has no
+other way to find out who they're looking at. Regression: the detail page
+badge showed "RT: Unassigned" for the assigned operator themselves."""
+
+from app.models.test import Test
+from app.models.technique import Technique
+
+
+def _seed_technique(db) -> Technique:
+    technique = Technique(
+        mitre_id="T9996", name="Assignee Username Test Technique",
+        tactic="execution", platforms=["linux"],
+    )
+    db.add(technique)
+    db.commit()
+    db.refresh(technique)
+    return technique
+
+
+def _seed_test(db, technique, created_by, **overrides) -> Test:
+    test = Test(technique_id=technique.id, name="Assignee username test", created_by=created_by, **overrides)
+    db.add(test)
+    db.commit()
+    db.refresh(test)
+    return test
+
+
+def test_red_tech_assignee_username_resolved_for_the_assigned_operator(
+    client, db, red_tech_headers, red_tech_user, red_lead_user,
+):
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, red_lead_user.id, red_tech_assignee=red_tech_user.id)
+
+    resp = client.get(f"/api/v1/tests/{test.id}", headers=red_tech_headers)
+
+    assert resp.status_code == 200, resp.text
+    body = resp.json()
+    assert body["red_tech_assignee"] == str(red_tech_user.id)
+    assert body["red_tech_assignee_username"] == red_tech_user.username
+
+
+def test_blue_tech_assignee_username_resolved(client, db, red_lead_headers, red_lead_user, blue_tech_user):
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, red_lead_user.id, blue_tech_assignee=blue_tech_user.id)
+
+    resp = client.get(f"/api/v1/tests/{test.id}", headers=red_lead_headers)
+
+    assert resp.status_code == 200, resp.text
+    assert resp.json()["blue_tech_assignee_username"] == blue_tech_user.username
+
+
+def test_assignee_username_is_none_when_unassigned(client, db, red_lead_headers, red_lead_user):
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, red_lead_user.id)
+
+    resp = client.get(f"/api/v1/tests/{test.id}", headers=red_lead_headers)
+
+    assert resp.status_code == 200, resp.text
+    body = resp.json()
+    assert body["red_tech_assignee"] is None
+    assert body["red_tech_assignee_username"] is None