refactor: Restructure project into core, services, ui, and utils directories, moving existing modules and adding new UI tabs.

core/state.py

@@ -0,0 +1,21 @@
+import threading
+from typing import Optional
+from services.novel_generator import NovelGenerator, get_generator, NovelProject
+
+class AppState:
+    """Trạng thái ứng dụng dùng chung giữa các tab"""
+    def __init__(self):
+        self.is_generating = False
+        self.stop_requested = False
+        self.lock = threading.Lock()
+        self.current_project: Optional[NovelProject] = None
+        self.generator: Optional[NovelGenerator] = None
+
+    def get_generator(self) -> NovelGenerator:
+        """Lấy hoặc tạo generator"""
+        if self.generator is None:
+            self.generator = get_generator()
+        return self.generator
+
+# Global app state singleton
+app_state = AppState()