修复版本1.0.7的若干问题 (#11)

* fix/ 0:00 audio ui

* fix/ persist memoir image state and collapse voice history

Keep generated chapter images from staying in processing after successful uploads, and restore segmented voice recordings as a single audio message when reopening conversations.

Made-with: Cursor

* fix/ persist local conversation state and stabilize voice UI

Keep CreateMemory conversations driven by Room so recent text and audio survive page exits, and prevent stale 0:00 voice bubbles while list ordering follows the latest local message time.

Made-with: Cursor

* fix/ server-side root cause for conversation list time and message timestamps

- Add Conversation.last_message_at column with migration and index
- Update last_message_at on text message, audio segment, and AI response
- Sort conversation list by COALESCE(last_message_at, started_at) DESC
- Return real per-message timestamps from Redis history instead of now()
- Pass user_message_timestamp through agent pipeline to avoid LLM delay skew
- Remove all debug logging from server, client, and CI workflow
- Restore import json in conversation_agent (was broken by debug removal)
- Client: remove DebugRuntimeLogger, stop sending transcript as text message

Made-with: Cursor

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Co-authored-by: Kevin <kevin@brighteng.org>

api/tests/test_websocket_baseline.py

@@ -210,6 +210,7 @@ class WebSocketBaselineTest(unittest.IsolatedAsyncioTestCase):
         self.assertEqual(len(segments), 1)
         self.assertEqual(segments[0].transcript_text, "你好")
         self.assertIsNone(segments[0].audio_url)
+        self.assertIsNotNone(conversation.last_message_at)
         fake_manager.background_runner.queue_message.assert_awaited_once()
         process_user_message_mock.assert_awaited_once()
 
@@ -269,6 +270,7 @@ class WebSocketBaselineTest(unittest.IsolatedAsyncioTestCase):
         self.assertEqual(len(segments), 1)
         self.assertEqual(segments[0].transcript_text, "这是转写结果")
         self.assertEqual(segments[0].audio_url, "audio:12s")
+        self.assertIsNotNone(conversation.last_message_at)
 
         transcript_msgs = [
             item["message"]