fix(ui): improve dropdown positioning and empty backup states

Refactor dropdown behavior, add sorted resource selection to breadcrumbs, and show an empty state when no backup executions exist.

resources/css/app.css

@@ -1939,27 +1939,7 @@ html[data-theme="custom"] textarea:disabled {
     box-shadow: 0 12px 32px rgba(0, 0, 0, 0.45);
 }
 
-.floating-dropdown-panel {
-    min-width: 0;
-}
-
-/* Older menus still render inside their page container. On mobile, keep
-   those panels fully visible until they are migrated to the portaled
-   dropdown component. Portaled panels carry their own fixed coordinates. */
 @media (max-width: 767px) {
-    .listbox-panel:not([style*="position: fixed"]) {
-        position: fixed !important;
-        top: 50% !important;
-        right: auto !important;
-        left: 50% !important;
-        width: max-content;
-        max-width: calc(100vw - 1.5rem) !important;
-        max-height: calc(100dvh - 1.5rem) !important;
-        box-sizing: border-box;
-        transform: translate(-50%, -50%) !important;
-        z-index: 9999 !important;
-    }
-
     /* The mobile top bar's backdrop filter makes it the containing block for
        fixed descendants. Keep this menu anchored below its trigger instead
        of centering it within the short top bar. */