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

tests/test_core/test_server.py

@@ -0,0 +1,57 @@
+import pytest
+import os
+import tempfile
+
+os.environ["DEEPSEEK_API_KEY"] = "fake-test-key"
+
+
+class TestCoreImport:
+    def test_import_backend_server(self):
+        from core import BackendServer
+        assert BackendServer is not None
+
+    def test_import_backend_client(self):
+        from core import BackendClient
+        assert BackendClient is not None
+
+    def test_import_embedded_db(self):
+        from core import EmbeddedGraphDB
+        assert EmbeddedGraphDB is not None
+
+
+class TestBackendServer:
+    def test_create_server(self):
+        from core import BackendServer
+        server = BackendServer(db_path=":memory:", use_embedded_db=True)
+        assert server is not None
+        assert server._running is False
+
+    def test_start_server(self):
+        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")
+            
+            assert server._running is True
+            assert server._graph is not None
+            
+            server.shutdown()
+        finally:
+            if os.path.exists(db_path):
+                os.unlink(db_path)
+
+    def test_shutdown(self):
+        from core import BackendServer
+        with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+            db_path = f.name
+        
+        server = BackendServer(db_path=db_path, use_embedded_db=True)
+        server.start(api_key="", base_url="https://api.test.com")
+        
+        assert server._running is True
+        
+        server.shutdown()
+        assert server._running is False