refactor(ui): add LabeledInputRow + LabeledInputMultiline; complete inputs layer

Extend the inputs layer with the two remaining form-field idioms, pixel-identical:
- material::LabeledInputRow(label, labelPos, ...) — horizontal label-beside-input
  (Text + SameLine + SetNextItemWidth + InputText). Adopt at the settings RPC
  host/port/user/pass rows.
- material::LabeledInputMultiline(label, id, buf, size, flags) — label above a
  sized multiline input. Adopt at the address-book notes and request-payment
  memo (drops the redundant SetNextItemWidth that InputTextMultiline's explicit
  size already governs).

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

src/ui/windows/request_payment_dialog.cpp

@@ -206,9 +206,8 @@ void RequestPaymentDialog::render(App* app)
         // Memo (optional, only for z-addr)
         bool is_zaddr = (s_address[0] == 'z');
         if (is_zaddr) {
-            ImGui::Text("%s", TR("request_memo"));
-            ImGui::SetNextItemWidth(-1);
-            if (ImGui::InputTextMultiline("##Memo", s_memo, sizeof(s_memo), ImVec2(-1, memoInput.height > 0 ? memoInput.height : 60))) {
+            if (material::LabeledInputMultiline(TR("request_memo"), "##Memo", s_memo, sizeof(s_memo),
+                                                ImVec2(-1, memoInput.height > 0 ? memoInput.height : 60))) {
                 s_uri_dirty = true;
             }
         } else {