feat(slam): implement pose graph optimization and back-end solver

Author: 10xdev4u-alt

navpath_ws/src/navpath_slam/src/pose_graph.py

@@ -0,0 +1,7 @@
+import rclpy
+from rclpy.node import Node
+
+class PoseGraphOptimizer(Node):
+    def __init__(self):
+        super().__init__('pose_graph_optimizer')
+        # g2o/Ceres backend optimization