fix(gui): keep the viewer Paste row a single line, not a full-height block

The Paste button + code field were wrapped in `with_layout(right_to_left)`,
which grabs the parent's entire remaining height and vertically centers the
row in it — gutting the View screen (field dropped to the middle, button
pinned far right). Use a plain `ui.horizontal` row with the button first and
the field filling the rest via INFINITY width. Same one-click-paste behavior,
correct single-row layout.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/gui/mod.rs

@@ -595,11 +595,12 @@ impl PixelPassApp {
 
         ui.label("Paste the share code you received:");
         ui.add_space(4.0);
-        // Field fills the row, with a Paste button pinned to its right — the
-        // read-side mirror of the host's Copy button (one click grabs the code
-        // the host just put on the clipboard).
+        // A Paste button (read-side mirror of the host's Copy button — one
+        // click grabs the code the host just put on the clipboard) with the
+        // field filling the rest of the row. A single horizontal row, so it
+        // doesn't grab the panel's full height.
         let ticket_resp = ui
-            .with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
+            .horizontal(|ui| {
                 if ui.button("📋 Paste").clicked()
                     && let Some(text) = get_clipboard()
                 {