C1: Register tasks_bp in app.py

- Blueprint tasks_bp registrado para endpoints /pos/api/tasks/*
- Tests: 73/73 pasando

pos/app.py

@@ -86,6 +86,9 @@ def create_app():
     from blueprints.public_api_bp import public_api_bp
     app.register_blueprint(public_api_bp)
 
+    from blueprints.tasks_bp import tasks_bp
+    app.register_blueprint(tasks_bp)
+
     # Health check
     @app.route('/pos/health')
     def health():