feat(ux): copy-to-clipboard confirmations + scale wizard buttons for HiDPI

Feedback-convention + HiDPI cleanup (from the audit's living-hygiene threads):
- Copy actions that were silent now toast a confirmation: transaction
  address/txid (context menu, click-to-copy, detail buttons), peer and banned-
  peer addresses, the Settings data-dir copy, the chat message "Copy", and the
  key-export result copy.
- The first-run wizard's Skip/Back buttons used raw ImVec2(120/80,0) widths that
  rendered tiny at HiDPI; they now multiply by ui::Layout::dpiScale().

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/windows/peers_tab.cpp

@@ -776,9 +776,11 @@ void RenderPeersTab(App* app)
                         ImGui::Separator();
                         if (ImGui::MenuItem(TR("copy_address"))) {
                             ImGui::SetClipboardText(peer.addr.c_str());
+                            ui::Notifications::instance().info(TR("copied_to_clipboard"));
                         }
                         if (ImGui::MenuItem(TR("peers_copy_ip"))) {
                             ImGui::SetClipboardText(ExtractIP(peer.addr).c_str());
+                            ui::Notifications::instance().info(TR("copied_to_clipboard"));
                         }
                         ImGui::Separator();
                         if (ImGui::MenuItem(TR("peers_ban_24h"))) {
@@ -892,6 +894,7 @@ void RenderPeersTab(App* app)
                     if (effects::ImGuiAcrylic::BeginAcrylicContextItem(nullptr, 0, acrylicTheme2.menu)) {
                         if (ImGui::MenuItem(TR("copy_address"))) {
                             ImGui::SetClipboardText(banned.address.c_str());
+                            ui::Notifications::instance().info(TR("copied_to_clipboard"));
                         }
                         if (ImGui::MenuItem(TR("peers_unban"))) {
                             app->unbanPeer(banned.address);