refactor(ui): consolidate dialog footers + shared empty-state, unify buttons/rounding

Addresses the cross-screen inconsistencies from the layout audit by routing screens onto
the design system's own (previously under-used) shared helpers:

- Dialog footers: migrate ~9 overlay dialogs off hand-rolled placement onto the shared
  helpers — DialogActionFooter (primary+Close), DialogConfirmFooter, or
  BeginOverlayDialogFooter for custom/multi-button rows — so footers share one centered
  treatment. All footer/action buttons now use TactileButton (glass press) instead of the
  bare StyledButton some dialogs used.
- Empty states: add a shared material::DrawEmptyState(icon, title, hint) (centered icon +
  title + wrapped hint) and adopt it in Peers, Transactions, and Market-portfolio, which
  previously showed a bare left-aligned caption.
- Security dialogs: add the missing Cancel to Change Passphrase and Set PIN so the whole
  security family shares a two-button footer (Cancel dismisses without applying).
- Transactions pager: shared TactileButton helpers (matching Explorer).
- Frosted-pane rounding: Contacts/Chat use Layout::glassRounding() instead of hardcoded
  12/10/8px literals, matching Peers.
- "Set Label..." title loses its stray trailing ellipsis.

Preserves every button's label and action; the transfer footer's order becomes
[Confirm][Cancel] to match the shared helper's primary-first convention. Verified at 1280
across full-node + Lite + Windows (ctest green) and an adversarial diff review (clean).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ui/windows/request_payment_dialog.cpp

@@ -224,6 +224,10 @@ void RequestPaymentDialog::render(App* app)
             if (w_uri  < actionBtn.width) w_uri  = actionBtn.width;
             if (w_addr < actionBtn.width) w_addr = actionBtn.width;
 
+            // Center the two-button copy row via the shared helper (no extra divider; the Separator
+            // above already frames this region). Total = both button widths + the ItemSpacing between.
+            material::BeginOverlayDialogFooter(w_uri + w_addr + ImGui::GetStyle().ItemSpacing.x, false);
+
             // Copy URI button
             if (material::TactileButton(TR("request_copy_uri"), ImVec2(w_uri, 0), btnFont)) {
                 ImGui::SetClipboardText(s_payment_uri.c_str());
@@ -248,6 +252,9 @@ void RequestPaymentDialog::render(App* app)
             float w_close = ImGui::CalcTextSize(TR("close")).x + btnPad;
             ImGui::PopFont();
             if (w_close < actionBtn.width) w_close = actionBtn.width;
+            // Center the lone Close button via the shared helper (no extra divider — matches the
+            // existing tight spacing above it).
+            material::BeginOverlayDialogFooter(w_close, false);
             if (material::TactileButton(TR("close"), ImVec2(w_close, 0), btnFont)) {
                 s_open = false;
             }