Add Collector exclusion commands

[Hippoom]

Summary

• Adds /dfrl collector commands to list, exclude, re-add, and reset minimap button exclusions.
• Persists excluded minimap button names in the Collector settings.
• Releases excluded buttons from Collector ownership and skips them during future scans.
• Documents the new commands in the README.

Test plan

• Used /dfrl collector list to show known minimap buttons.
• Used /dfrl collector del <ButtonName> to release a button from the Collector.
• Reloaded the UI and verified the excluded button stayed outside the Collector.
• Used /dfrl collector add <ButtonName> to let Collector manage the button again.
• Used /dfrl collector reset to clear exclusions.

Fixes #24