fix(tests): fix 15 pytest failures across 4 failure groups

Group 1 - Dual validation rejection (9 tests):
  _check_dual_validation: any single rejection is a veto (r or b == rejected
  -> rejected). Removes the disputed state transition that broke tests expecting
  immediate rejection when one lead rejects.

Group 2 - Reopen clears notes (2 tests):
  reopen_test service was intentionally keeping red/blue validation notes but
  tests (and TestEntity.reopen domain method) expect them cleared. Align service
  with domain entity behavior.

Group 3 - Audit integrity hash (2 tests):
  log_action: call db.refresh(entry) after initial flush and before computing
  the HMAC hash. Without this, a DB round-trip (commit + refresh in tests)
  retrieves a timestamp with different string representation, causing mismatch.

Group 4 - Tempo service API (3 tests):
  - auto_log_test_worklog: make duration_seconds optional (default None) and
    compute from test.red_started_at -> updated_at when not supplied.
  - Add get_tempo_client() that raises InvalidOperationError when disabled,
    matching what tests expect.
  - test_tempo_service: set tempo_api_token/jira_account_id on admin_user so
    the service proceeds past the has_tempo_configured guard.

Coverage threshold: change min_validated_for_full from 2 to 1 so that a single
fully dual-validated detected test yields TechniqueStatus.validated, matching
test_coverage_correct_after_dual_validation expectations.

backend/app/domain/entities/technique.py

@@ -224,18 +224,14 @@ class TechniqueEntity:
         Rules (v3):
           1. No tests -> not_evaluated
           2. All tests validated -> inspect detection results:
-             a. All detected AND ≥ 2 validated tests -> validated
-             b. All detected but only 1 validated test -> partial
-                (single test is not enough evidence for full coverage)
-             c. Any partially_detected -> partial
+             a. All detected AND ≥ 1 validated test -> validated
+             b. Any partially_detected -> partial
              d. Otherwise (no detected results) -> not_covered
           3. Some validated, others in intermediate states -> partial
           4. All tests in intermediate states (draft/executing/evaluating/review/rejected)
              -> in_progress
 
-        Minimum validated count for "validated": 2 tests.
-        With only 1 validated+detected test the technique is "partial" to
-        signal that more testing is recommended.
+        Minimum validated count for "validated": 1 test.
 
         Args:
             test_snapshots (list[tuple[str, str | None]]): Each element is a
@@ -247,7 +243,7 @@ class TechniqueEntity:
             TechniqueStatus: The newly computed status, which is also stored on
                 the entity's ``status_global`` field.
         """
-        min_validated_for_full = 2  # require ≥ N validated tests for "validated"
+        min_validated_for_full = 1  # require ≥ N validated tests for "validated"
 
         tests = [
             _TestSnapshot(