refactor(ios): drop UIApplication.sendAction keyboard dismiss for binding-driven focus

[datlechin]

Summary

P1 #7: replace the imperative UIApplication.shared.sendAction(#selector(UIResponder.resignFirstResponder), ...) keyboard dismiss in QueryEditorView.executeQueryDirect with a SwiftUI @Binding<Bool> focus channel into SQLHighlightTextView.

What changes:

• SQLHighlightTextView (UIViewRepresentable) gains an @Binding var isFocused: Bool parameter (default .constant(false) so existing call sites that don't care still compile)
• updateUIView syncs the binding into the wrapped UITextView via becomeFirstResponder() / resignFirstResponder() only when state actually diverges
• Coordinator gains textViewDidBeginEditing and textViewDidEndEditing to propagate user-driven focus changes back to the binding
• QueryEditorView adds @State private var editorFocused = false, passes $editorFocused into the editor, and sets editorFocused = false before executing a query, dismissing the keyboard

Why a plain @State Bool and not @FocusState: @FocusState's projected value is FocusState<Bool>.Binding, which doesn't satisfy @Binding var isFocused: Bool. The canonical iOS pattern for UIViewRepresentable focus is parent @State Bool plus two-way sync through the representable's update method and delegate callbacks. The user-visible behavior matches @FocusState: keyboard dismisses declaratively when state flips to false.

Two resignFirstResponder() calls remain inside SQLHighlightTextView itself: one in updateUIView (sync from binding) and one in the toolbar Done button's @objc handler. Both are UIKit-internal and not the imperative SwiftUI escape hatch this PR targets.

Test plan

• Tap into the SQL editor: keyboard appears, editorFocused becomes true (verify by adding a .onChange print if needed)
• Tap "Run": keyboard dismisses immediately, query executes
• Tap "Done" on the editor's input accessory toolbar: keyboard dismisses, editorFocused becomes false via textViewDidEndEditing
• Tap into another control (e.g., switch to History tab): keyboard dismisses, focus state stays consistent
• Switch tabs and come back: typing into the editor still works, no stuck focus