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

backend/db/conexion.py

@@ -1,6 +1,6 @@
 # backend/db/conexion.py
 from entrypoint.init_db import db_credencial
-from src.ConexionSql.Postgres_conexion import PostgresConexion
+from domains.ConexionSql.Postgres_conexion import PostgresConexion
 
 def get_conexion():
     conexion = PostgresConexion(db_credencial)