Add environment status API and CLI command

[dive2tech]

Summary

• Add public API helpers to inspect active environments and multi-instance pools.
• Introduce afs status CLI command for human-readable and JSON status output.
• Include tests for API helpers and CLI behavior, including the tabulate fallback.

Implementation details

• affinetes.api:
  • get_environment_status(env_id, include_stats=True): returns JSON-serializable status for a single environment, including readiness and optional pool stats.
  • get_all_environment_statuses(include_stats=True): aggregates status for all active environments from the global registry.
• affinetes.cli:
  • New afs status [NAME] [--json] [--verbose] command in cli/main.py.
  • Implementation in cli/commands.py:
    • Uses the new API helpers.
    • Supports table output via tabulate if available, otherwise a manual ASCII table fallback.
    • --json outputs raw JSON.
    • --verbose prints per-instance host/port/request counts for pools.
• Tests:
  • tests/test_api_status.py: unit tests for the new API helpers (single env, pools, include_stats flag, aggregation).
  • tests/test_cli_status.py: tests CLI behavior including no envs, missing env name, JSON output, table fallback, and verbose instance details.

Test plan

• Unit tests:
  • pytest tests/test_api_status.py tests/test_cli_status.py
• Manual tests:
  • Start an environment:
    • afs run <image> --name test-env
  • Verify CLI:
    • afs status
    • afs status --json
    • afs status --verbose