Add harness authentication snapshots

[firewalker06]

Implements Fizzy #236.

• Adds on-demand authentication checks for built-in and custom harness profiles.
• Persists only authenticated, unauthenticated, or unknown state plus check time.
• Shows an explicit snapshot and per-harness action menu in Settings.
• Keeps raw harness output, credentials, and custom command details out of persisted snapshots and API payloads.

Validation:

• bundle exec ruby test/harness_auth_check_test.rb
• bundle exec ruby test/harness_catalog_test.rb
• bundle exec ruby test/remote_server_test.rb
• bin/test (running)
• bin/remote-ui-smoke was extended with desktop/mobile auth snapshot coverage and captures.