Add confirmation dialog before overwriting albums

Summary

• Clicking "Overwrite" previously executed immediately with no confirmation, which is dangerous
• Added an OverwriteConfirmDialog modal (same pattern as DeleteConfirmDialog) that warns before replacing the existing album
• Cancel dismisses the dialog; Overwrite in the dialog proceeds with the sort

Test plan

• Navigate to an album that conflicts with an existing sorted album
• Click "Overwrite" — confirmation dialog should appear
• Click "Cancel" — dialog closes, nothing happens
• Click "Overwrite" in dialog — album is sorted with overwrite

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