Add word-level timestamps and confidence scores

- New word_timestamps option (default False) in client handshake
- When enabled, each segment includes 'words' array with per-word
  start/end times and probability scores
- Wired through entire pipeline: client → server → backend → transcribe()
- Words include timestamp_offset for accurate absolute times
- REST API already supported word timestamps; now WebSocket does too
- Added 9 unit tests for word timestamp extraction and formatting

tests/test_client.py

@@ -43,24 +43,25 @@ class TestClientWebSocketCommunication(BaseTestCase):
 
 class TestClientCallbacks(BaseTestCase):
     def test_on_open(self):
-        expected_message = json.dumps({
-            "uid": self.client.uid,
-            "language": self.client.language,
-            "task": self.client.task,
-            "model": self.client.model,
-            "use_vad": True,
-            "send_last_n_segments": 10,
-            "no_speech_thresh": 0.45,
-            "clip_audio": False,
-            "same_output_threshold": 10,
-            "enable_translation": False,
-            "target_language": "fr",
-            "hotwords": None,
-            "enable_diarization": False,
-            "max_speakers": 10,
-        })
+
         self.client.on_open(self.mock_ws_app)
-        self.mock_ws_app.send.assert_called_with(expected_message)
+        self.mock_ws_app.send.assert_called_once()
+        sent_message = json.loads(self.mock_ws_app.send.call_args[0][0])
+        self.assertEqual(sent_message["uid"], self.client.uid)
+        self.assertEqual(sent_message["language"], self.client.language)
+        self.assertEqual(sent_message["task"], self.client.task)
+        self.assertEqual(sent_message["model"], self.client.model)
+        self.assertTrue(sent_message["use_vad"])
+        self.assertEqual(sent_message["send_last_n_segments"], 10)
+        self.assertAlmostEqual(sent_message["no_speech_thresh"], 0.45)
+        self.assertFalse(sent_message["clip_audio"])
+        self.assertEqual(sent_message["same_output_threshold"], 10)
+        self.assertFalse(sent_message["enable_translation"])
+        self.assertEqual(sent_message["target_language"], "fr")
+        self.assertIsNone(sent_message["hotwords"])
+        self.assertFalse(sent_message["enable_diarization"])
+        self.assertEqual(sent_message["max_speakers"], 10)
+        self.assertFalse(sent_message["word_timestamps"])
 
     def test_on_message(self):
         message = json.dumps(