feat(monitors): add folder management commands

[UlricQin]

Add monit folder-health, folder-create, folder-update, folder-move, and folder-delete alongside folder-list, using typed SDK methods. Regenerate command help, operation coverage, and the Monitors skill card.

Pin go-flashduty to v0.15.18-0.20261015103612-f84d9ddaca1a, the SDK PR commit, so a normal checkout builds and tests without a local workspace or replace directive. Switch to the official SDK release when available.

Validation:

• GOWORK=off go test ./... passed.
• GOWORK=off go run ./internal/cmd/skilldoc check passed.
• Folder command tests cover all six routes, updating fields, moving to the root with explicit zero, and rejecting an omitted move destination before sending a request.

Related PRs:

• SDK: feat(monitors): add public folder management APIs go-flashduty#102
• Gateway: https://github.com/flashcatcloud/fc-pgy/pull/1273
• API documentation: docs(monitors): document public folder management APIs flashduty-docs#1058

Release coordination: merge and publish the SDK first, then release the CLI. Register and reload the gateway configuration in each target environment before using the new commands there. No runtime environment was modified by this PR.