- Introduce `cnpg_placement.py` to handle round-robin node assignments for CloudNativePG clusters.
- Implement persistent placement plans with schema normalization and hashing.
- Add `load_cnpg_placement_plan` and `save_cnpg_placement_plan` for plan persistence.
- Integrate planner with installer to support node-based topology configuration.
- Update `actions.py` with placement planning logic, including rebalance support and node eligibility checks.
- Extend shell utilities (`init_cloudnative_pg.sh`) for placement-aware CNPG topology adjustments.
- Add comprehensive unit tests and integration tests for planner functionality, persistence, and shell environment exports.
