Toast action results and confirm destructive actions in one dialog

Inline banners and per-row status text reported action results all over
the app; they are replaced by a small toast stack (bottom-right, Level 3
floating well styling) that only speaks for actions: successes fade,
errors stay until dismissed, and form-field validation stays inline.

Destructive actions no longer use bespoke inline confirm steps (the
library detail's Confirm delete button) or fire immediately (duplicate
copies/items, delete page selections, temp cleanup, upload discard, job
cancellation): they all go through one promise-based confirm dialog
(confirmAction) with a danger variant, Escape/backdrop to cancel.

frontend/src/features/optimize/OptimizeModal.tsx

@@ -19,6 +19,7 @@ import {
   type OptimizeOptions,
 } from "./types";
 import { useOptimizer } from "./useOptimizer";
+import { toast } from "@/store/toasts";
 
 const DIMENSION_CHOICES: { value: number | null; label: string }[] = [
   { value: null, label: "Keep original" },
@@ -248,12 +249,17 @@ export function OptimizeModal({
       if (result?.storageKey) void deleteStoredFile(result.storageKey);
       setApplied(true);
       setApplyError(null);
+      toast.ok(`${item.j_id} optimized.`);
       void queryClient.invalidateQueries({ queryKey: ["file", item.j_id] });
       void queryClient.invalidateQueries({ queryKey: ["files"] });
       void queryClient.invalidateQueries({ queryKey: ["storage"] });
       void queryClient.invalidateQueries({ queryKey: ["duplicates-md5"] });
     },
-    onError: (err) => setApplyError(errorMessage(err)),
+    onError: (err) => {
+      const message = errorMessage(err);
+      setApplyError(message);
+      toast.error(message);
+    },
   });
 
   const originalSize = item.size;