feat: ✨ add Display settings tab with stacked query results option

[AustralianRaven]

Summary

• Adds a Display tab to the Settings modal (first tab, opens by default)
• New "Results Layout" setting with two options:
  • Tabs (default) — existing behaviour, one result at a time with the status bar dropdown to switch
  • Stacked — all result sets rendered vertically as separate tables after a multi-query run
• Each stacked result block has its own Download / Copy to Clipboard menu scoped to that result
• The global Download button in the status bar is hidden when Stacked mode is active
• Setting is persisted via the existing appdb/setting store (queryResultsLayout key)

[justinnnb]

Looks good I think