Add --dry-run to secrets set/delete to preview changes before applying #331

Problem

infisical secrets set and infisical secrets delete apply changes to the backend immediately — there's no way to preview exactly what will be created, updated, or deleted first. This matters most in CI/scripted secret-rotation pipelines, where a preview step (à la terraform plan) is a standard safety net before mutating state.

Proposal

Add a --dry-run flag to infisical secrets set and infisical secrets delete (and optionally folders create/folders delete) that:

• Computes the exact set of operations that would be performed (create / update / delete, with masked values) using the existing logic that already separates "compute operations" from "execute + print" in packages/cmd/secrets.go.
• Prints the same table/JSON output the real run would produce, but skips the actual SetRawSecrets/CallDeleteSecretsRawV3 API call.
• Exits 0 without mutating anything.

Scope

Since secrets.go already builds a secretOperations-style list before calling the API and before printing results, this should be a small, additive change: gate the actual API call behind if !dryRun, and note in the output that it was a dry run. No changes needed to the API client or other commands. Happy to open a PR.