Refactor: split services.py into services/ package

ChatService → services/chat.py
DocumentService → services/document.py
TTSService → services/tts.py
services/__init__.py re-exports all three for backward-compatible imports

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.idea/modules.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/.idea/youlbot-webui.iml" filepath="$PROJECT_DIR$/.idea/youlbot-webui.iml" />
+    </modules>
+  </component>
+</project>