Support Multiple MQTT Broker Profiles Safely

[Dumdart]

Summary

Enable simultaneous MQTT repositories for multiple broker profiles while keeping the active profile’s runtime state synchronized. Sanitize broker credentials exposed to the UI and preserve stored passwords during updates.

Changes

Bug Fixes

• Preserve configured passwords when editing broker settings without re-entering them.
• Move live message and connection observation when switching broker profiles.

Features

• Add safe BrokerSummary values that omit password contents.
• Support per-profile MQTT repositories, topic listing, and broker switching.
• Mask configured passwords in the broker settings dialog.

Refactoring

• Centralize active repository lifecycle and profile management in TopicGateRuntime.
• Update view models and GUI components to use broker summaries.

Improvements

• Add coverage for credential sanitization, password preservation, profile switching, and masked UI fields.

Testing

• Added and updated unit and GUI tests covering multi-profile runtime behavior and credential handling.
• Not run (not requested).