feat(ui): add setting to keep the action bar visible while scrolling (#1095)

Adds a 'Keep Action Bar Visible' toggle (default off) under
Settings > Interface > Layout Settings. When enabled, the controls bar
(Refresh, Download, etc.) and the breadcrumb nav are wrapped in a shared
sticky container (.sticky-topbar) so both stay pinned as one unit; when
disabled, the wrapper is display: contents and the original behavior
(only the breadcrumb stays visible) is preserved.

locales/zh-TW.json

@@ -484,6 +484,8 @@
         "layoutSettings": {
             "groupByModel": "按模型分組",
             "groupByModelHelp": "啟用後，每個 CivitAI 模型僅顯示最新版本的單張卡片，舊版本將被隱藏。",
+            "stickyControls": "保持操作列可見",
+            "stickyControlsHelp": "啟用後，操作列（重新整理、下載等）會在捲動時與麵包屑導覽一起固定在頁面頂端。",
             "displayDensity": "顯示密度",
             "displayDensityOptions": {
                 "default": "預設",