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/similar/SimilarPage.tsx

@@ -21,6 +21,7 @@ import {
 import { formatBytes, formatDate } from "@/lib/format";
 import type { SimilarityCheck } from "@/lib/types";
 import { useE621 } from "@/store/e621";
+import { toast } from "@/store/toasts";
 
 const VIDEO_RE = /\.(mp4|webm)$/i;
 
@@ -39,12 +40,10 @@ export default function SimilarPage() {
   const [check, setCheck] = useState<SimilarityCheck | null>(null);
   const [uploading, setUploading] = useState(false);
   const [percent, setPercent] = useState(0);
-  const [error, setError] = useState<string | null>(null);
   const [dragging, setDragging] = useState(false);
 
   const [iqdb, setIqdb] = useState<E621IqdbResult[] | null>(null);
   const [iqdbBusy, setIqdbBusy] = useState(false);
-  const [iqdbError, setIqdbError] = useState<string | null>(null);
   const [selected, setSelected] = useState<E621IqdbResult | null>(null);
 
   const configured = Boolean(credentials?.configured);
@@ -57,10 +56,10 @@ export default function SimilarPage() {
       setFile(null);
       setIqdb(null);
       setSelected(null);
-      setError(null);
-      setIqdbError(null);
       if (inputRef.current) inputRef.current.value = "";
+      toast.ok("Temporary copy deleted.");
     },
+    onError: (error) => toast.error(errorMessage(error)),
   });
 
   async function startCheck(selectedFile: File) {
@@ -68,8 +67,6 @@ export default function SimilarPage() {
     setCheck(null);
     setIqdb(null);
     setSelected(null);
-    setError(null);
-    setIqdbError(null);
     setPercent(0);
     setUploading(true);
     try {
@@ -82,7 +79,7 @@ export default function SimilarPage() {
       setCheck(data);
       void queryClient.invalidateQueries({ queryKey: ["files"] });
     } catch (err) {
-      setError(errorMessage(err));
+      toast.error(errorMessage(err));
     } finally {
       setUploading(false);
     }
@@ -98,7 +95,7 @@ export default function SimilarPage() {
       );
       setIqdb(results);
     } catch (err) {
-      setIqdbError(e621ErrorMessage(err));
+      toast.error(e621ErrorMessage(err));
     } finally {
       setIqdbBusy(false);
     }
@@ -183,8 +180,6 @@ export default function SimilarPage() {
         </div>
       ) : null}
 
-      {error ? <p className="text-sm text-ctp-red">{error}</p> : null}
-
       {check ? (
         <div className="grid gap-6 lg:grid-cols-[320px_minmax(0,1fr)]">
           <aside className="flex flex-col gap-4">
@@ -359,8 +354,6 @@ export default function SimilarPage() {
                   </Link>{" "}
                   to reverse-search this image on e621.
                 </p>
-              ) : iqdbError ? (
-                <p className="mt-3 text-xs text-ctp-red">{iqdbError}</p>
               ) : iqdbBusy && !iqdb ? (
                 <div className="mt-3 flex justify-center py-4">
                   <Spinner className="h-4 w-4" />