Error handling added to MVP according to error_handling.md guideline

tests/services/test_worker.py

@@ -95,6 +95,9 @@ class TestWorkerFailurePath:
         assert transcript is not None
         assert transcript.text is None
         assert "provider failure" in transcript.error_detail
+        assert "[internal_unexpected_error]" in transcript.error_detail
+        assert "error_id=" in transcript.error_detail
+        assert "suggestion=" in transcript.error_detail
 
     def test_updates_existing_transcript_if_present(self, session, monkeypatch):
         """process_next_queued_job updates existing transcript instead of duplicating."""
@@ -118,6 +121,8 @@ class TestWorkerFailurePath:
         assert transcripts[0].id == existing.id
         assert transcripts[0].text is None
         assert "provider failure" in transcripts[0].error_detail
+        assert "[internal_unexpected_error]" in transcripts[0].error_detail
+        assert "error_id=" in transcripts[0].error_detail
 
 
 @pytest.mark.unit