feat: Implement main application shell with navigation and color scheme toggle

- Added Appshell component with responsive navbar and main content area
- Integrated ColorSchemeToggle for light/dark mode switching
- Created Welcome component with styled title and introductory text
- Developed ChatPage for LLM interaction with WebSocket support
- Implemented Biblioteca for managing notes with rich text editor
- Added LoginPage for user authentication with error handling
- Introduced MessageList and MessageBubble components for chat messages
- Styled components with CSS modules for consistent design

domains/Usuario/usuario.py

@@ -0,0 +1,15 @@
+class Usuario:
+    def __init__(self, id: int, nombre: str, email: str, activo: bool = True):
+        self.id = id
+        self.nombre = nombre
+        self.email = email
+        self.activo = activo
+
+    def activar(self):
+        self.activo = True
+
+    def desactivar(self):
+        self.activo = False
+
+    def __repr__(self):
+        return f"Usuario(id={self.id}, nombre='{self.nombre}', email='{self.email}', activo={self.activo})"