feat: Add option to disable automatic ephemeral resource creation

[mPokornyETM]

Summary

Adds a new global configuration option allowEphemeralResources that controls whether resources are automatically created when a job tries to lock a non-existent resource.

Fixes #651

Changes

• Added allowEphemeralResources boolean field to LockableResourcesManager (default: true for backward compatibility)
• Modified createResource() to check the setting before creating ephemeral resources
• Added UI configuration checkbox in the global settings
• Added help documentation for the new option
• Added JCasC (Configuration as Code) support
• Added comprehensive tests (7 new tests)

Behavior

Setting	Behavior
allowEphemeralResources: true (default)	Current behavior - resources are auto-created when locked
allowEphemeralResources: false	Jobs will block waiting for the resource to be manually created

Note: createResourceWithLabel() is not affected by this setting (allows explicit admin creation even when ephemeral resources are disabled).

Testing

• EphemeralResourcesOptionTest - 7 tests covering default behavior, disabled behavior, configuration toggles, and label-based locking
• ConfigurationAsCodeTest - JCasC integration verified

Supersedes

This is a clean implementation that supersedes #751 (which had merge conflicts and stale code).

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