🎨 Palette: Add dynamic labels and disabled state tooltips to main buttons

[acebytes]

💡 What: Added dynamic labels (Scanning..., Cleaning...) and .help() tooltips to the primary Scan and Clean buttons in ContentView.swift.
🎯 Why: Improves UX and accessibility by clearly explaining why a button is disabled (e.g., "Select at least one item to clean") and providing immediate textual feedback during async operations.
📸 Before/After: Buttons previously had static text and no tooltips. Now they show action progress and provide context on hover/focus.
♿ Accessibility: Tooltips (.help()) are read by VoiceOver and assist keyboard/mouse users in understanding disabled states and current background actions.

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PR created automatically by Jules for task 4939173087573018457 started by @acebytes

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