Phase 27: P2 quality improvements — logging, httpx pooling, validation, tests

- app.py: replace print() with logging, basicConfig with LOG_LEVEL env var
- api_client.py: shared AsyncClient instance (connection pooling), URL-encode
  delete_document path parameter, aclose() for cleanup
- services/document.py: validate file exists and extension before ingest
- tests/: ChatService (4) + DocumentService (6) unit tests via pytest-asyncio
- pyproject.toml: asyncio_mode = auto
- requirements-dev.txt: pytest, pytest-asyncio

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

tests/test_document_service.py

@@ -0,0 +1,56 @@
+import pytest
+from unittest.mock import AsyncMock, MagicMock
+
+from services.document import DocumentService
+
+
+@pytest.fixture
+def mock_api():
+    api = MagicMock()
+    api.ingest = AsyncMock(return_value={"chunks": 5})
+    api.list_documents = AsyncMock(return_value=["docs/report.pdf"])
+    api.delete_document = AsyncMock()
+    return api
+
+
+@pytest.fixture
+def service(mock_api):
+    return DocumentService(mock_api)
+
+
+async def test_ingest_valid_pdf(service, mock_api, tmp_path):
+    pdf = tmp_path / "report.pdf"
+    pdf.write_bytes(b"%PDF-1.4")
+    result = await service.ingest(str(pdf))
+    assert result == {"chunks": 5}
+    mock_api.ingest.assert_awaited_once_with(str(pdf))
+
+
+async def test_ingest_valid_txt(service, mock_api, tmp_path):
+    txt = tmp_path / "notes.txt"
+    txt.write_text("내용")
+    result = await service.ingest(str(txt))
+    assert result == {"chunks": 5}
+
+
+async def test_ingest_nonexistent_file_raises(service):
+    with pytest.raises(ValueError, match="파일을 찾을 수 없습니다"):
+        await service.ingest("/nonexistent/file.pdf")
+
+
+async def test_ingest_unsupported_extension_raises(service, tmp_path):
+    docx = tmp_path / "doc.docx"
+    docx.write_bytes(b"data")
+    with pytest.raises(ValueError, match="지원하지 않는 파일 형식"):
+        await service.ingest(str(docx))
+
+
+async def test_list_documents_delegates(service, mock_api):
+    result = await service.list_documents()
+    assert result == ["docs/report.pdf"]
+    mock_api.list_documents.assert_awaited_once()
+
+
+async def test_delete_document_delegates(service, mock_api):
+    await service.delete_document("/path/to/doc.pdf")
+    mock_api.delete_document.assert_awaited_once_with("/path/to/doc.pdf")