Perf: Initialize Sodium once at module import instead of per-cmdlet begin blocks

[MariusStorhaug]

Summary

Move initialization strategy toward module-load initialization so command hot paths avoid repeated init guard invocation.

Why

Current cmdlets call Initialize-Sodium in begin, which still adds function-call and guard-check overhead in tight loops.

Proposed change

• Initialize Sodium once during module import where safe.
• Keep idempotent fallback guard for robustness.
• Ensure initialization errors surface clearly at import time.

Acceptance criteria

• Module import initializes sodium successfully on supported platforms.
• Cmdlets no longer pay repeated init-check overhead in normal execution.
• Existing tests pass.
• Cold/warm benchmark data is captured to confirm behavior.