refactor: restructure to core/ + ui/ with multi-threaded backend

tests/test_ui.py

@@ -0,0 +1,70 @@
+import pytest
+import os
+import tempfile
+
+os.environ["DEEPSEEK_API_KEY"] = "fake-test-key"
+
+
+class TestUIImport:
+    def test_import_app(self):
+        from ui import GraphMemoryApp
+        assert GraphMemoryApp is not None
+
+    def test_import_config(self):
+        from ui import AppConfig
+        assert AppConfig is not None
+
+
+class TestUIApp:
+    def test_create_app(self):
+        from ui import GraphMemoryApp
+        app = GraphMemoryApp()
+        assert app is not None
+        assert app._backend_server is None
+        assert app._backend_client is None
+
+    def test_create_app_with_config(self):
+        from ui import GraphMemoryApp, AppConfig
+        
+        config = AppConfig(api_key="test-key", base_url="https://api.test.com")
+        app = GraphMemoryApp(config=config)
+        
+        assert app._config is config
+        assert app._config.api_key == "test-key"
+
+    def test_create_app_with_backend(self):
+        from ui import GraphMemoryApp
+        from core import BackendServer
+        
+        with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+            db_path = f.name
+        
+        try:
+            server = BackendServer(db_path=db_path, use_embedded_db=True)
+            server.start(api_key="", base_url="https://api.test.com")
+            
+            app = GraphMemoryApp(backend_server=server)
+            
+            assert app._backend_server is server
+            assert app._backend_client is not None
+            
+            server.shutdown()
+        finally:
+            if os.path.exists(db_path):
+                os.unlink(db_path)
+
+
+class TestAppConfig:
+    def test_config_from_env(self):
+        from ui import AppConfig
+        
+        config = AppConfig.from_env()
+        assert config is not None
+
+    def test_config_default_values(self):
+        from ui import AppConfig
+        
+        config = AppConfig()
+        assert config.api_key == ""
+        assert config.model == "deepseek-chat"
+        assert config.base_url == "https://api.deepseek.com"