Add lists/dicts demo, roadmap; remove temp file

Add a new Python example (Lists & Dictionaries.py) demonstrating list aliasing vs copy and basic dict methods (get, keys, values, items, pop). Add roadmap.md outlining a multi-phase Flutter→Full-Stack GenAI engineer roadmap covering Python, backend, APIs, RAG, and open-source model topics. Remove obsolete tempCodeRunnerFile.py.