Optimize Dijkstra and Prim's Algorithms Using Internal Node IDs

[prex03]

This PR introduces performance optimizations to the Dijkstra and Prim's algorithms by leveraging internal integer-based node IDs instead of string-based node names for graph traversal and indexing.

Changes Made

• Introduced internal name_to_id and id_to_name maps to translate between node names and integer IDs.
• Refactored Dijkstra and Prim implementations to use integer IDs for priority queues, adjacency lookups, and visited tracking.
• Preserved public interface and output format, user-facing interactions still use string-based node names and original edge weight types.