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>

services/document.py

@@ -0,0 +1,15 @@
+from api_client import APIClientProtocol
+
+
+class DocumentService:
+    def __init__(self, api_client: APIClientProtocol):
+        self._api = api_client
+
+    async def ingest(self, file_path: str) -> dict:
+        return await self._api.ingest(file_path)
+
+    async def list_documents(self) -> list[str]:
+        return await self._api.list_documents()
+
+    async def delete_document(self, source: str) -> None:
+        await self._api.delete_document(source)