feat(oxibadge): warn before losing unexported review edits, add undo

The review screen now tracks whether there are edits not yet exported
and asks for confirmation before discarding them: clicking back, or
closing the app window entirely (intercepted via onCloseRequested,
which needed a core:window:allow-destroy capability that wasn't
granted by core:default). The confirmation dialog (ConfirmDialog.svelte)
is generic, built on a shared ModalFrame extracted from ExportModal so
the two don't duplicate the backdrop/box styling.

Also adds undo: a per-row button (icon-only, left of the note, shown
when that day has edits) reverts just that day instantly, and a
per-employee "undo all" (icon in a red box, last among the header's
tools) reverts every day for the current employee after a confirmation
dialog, since that one can't be undone itself.

ActionButton moves out of review/ next to IconButton/PillButton, since
ConfirmDialog (outside the review feature) now uses it too.

Assisted-by: Claude Sonnet 5 <noreply@anthropic.com>

oxibadge/src/lib/components/review/EmployeeHeader.svelte

@@ -23,6 +23,7 @@
     onfixall,
     onaddlunchall,
     onroundall,
+    onundoall,
     onlyIssues = $bindable(false)
   }: {
     name: string;
@@ -41,6 +42,7 @@
     onfixall: () => void;
     onaddlunchall: () => void;
     onroundall: () => void;
+    onundoall: () => void;
     onlyIssues?: boolean;
   } = $props();
 
@@ -150,6 +152,21 @@
         >{$_('review.to_check_cap')}</button
       >
     </div>
+    {#if edits}
+      <IconButton
+        size="lg"
+        dangerFilled
+        ariaLabel={$_('review.undo_all')}
+        title={$_('review.undo_all_title')}
+        onclick={onundoall}
+      >
+        {#snippet icon()}
+          <svg width="18" height="18" viewBox="0 0 24 24" aria-hidden="true" style="stroke-width: 2"
+            ><path d="M9 14l-5-5 5-5" /><path d="M20 20v-7a4 4 0 0 0-4-4H4" /></svg
+          >
+        {/snippet}
+      </IconButton>
+    {/if}
   </div>
 </div>