feat(feed): reshuffle button for the "surprise me" sort

The backend shuffle sort already accepts a seed param. Add a circular
reshuffle button next to the sort control (shown only when shuffle is
active) that re-rolls the seed and re-queries the feed; selecting shuffle
also seeds a fresh order instead of the deterministic seed-0 one. The seed
lives in FeedFilters but is intentionally kept out of the URL state.

frontend/src/components/Sidebar.tsx

@@ -8,6 +8,7 @@ import {
   EyeOff,
   GripVertical,
   Pencil,
+  RefreshCw,
   RotateCcw,
   X,
 } from "lucide-react";
@@ -48,6 +49,9 @@ const SORT_IDS = [
 
 const SHOW_IDS = ["unwatched", "in_progress", "all", "watched", "saved", "hidden"];
 
+// Fresh shuffle token for the "surprise me" sort.
+const rollSeed = () => Math.floor(Math.random() * 1_000_000_000);
+
 const DATE_PRESETS: { days: number; key: string }[] = [
   { days: 1, key: "24h" },
   { days: 7, key: "1week" },
@@ -215,9 +219,19 @@ export default function Sidebar({
         );
       case "sort":
         return (
+          <div className="flex items-center gap-1.5">
             <select
               value={filters.sort}
-            onChange={(e) => setFilters({ ...filters, sort: e.target.value })}
+              onChange={(e) => {
+                const sort = e.target.value;
+                // Seed shuffle on selection so it lands on a fresh order, not the
+                // deterministic seed-0 one every time.
+                setFilters({
+                  ...filters,
+                  sort,
+                  seed: sort === "shuffle" ? rollSeed() : undefined,
+                });
+              }}
               className="w-full bg-card border border-border rounded-lg px-2 py-1.5 text-sm outline-none focus:border-accent"
             >
               {SORT_IDS.map((id) => (
@@ -226,6 +240,17 @@ export default function Sidebar({
                 </option>
               ))}
             </select>
+            {filters.sort === "shuffle" && (
+              <button
+                onClick={() => setFilters({ ...filters, seed: rollSeed() })}
+                title={t("sidebar.reshuffle")}
+                aria-label={t("sidebar.reshuffle")}
+                className="shrink-0 p-1.5 rounded-lg border border-border bg-card text-fg shadow-sm hover:border-accent hover:text-accent active:translate-y-px transition"
+              >
+                <RefreshCw className="w-4 h-4" />
+              </button>
+            )}
+          </div>
         );
       case "date":
         return (

frontend/src/i18n/locales/de/sidebar.json

@@ -23,6 +23,7 @@
   "from": "Von",
   "to": "Bis",
   "clearDates": "Daten löschen",
+  "reshuffle": "Neu mischen",
   "widget": {
     "show": "Anzeigen",
     "sort": "Sortierung",

frontend/src/i18n/locales/en/sidebar.json

@@ -23,6 +23,7 @@
   "from": "From",
   "to": "To",
   "clearDates": "clear dates",
+  "reshuffle": "Reshuffle",
   "widget": {
     "show": "Show",
     "sort": "Sort",

frontend/src/i18n/locales/hu/sidebar.json

@@ -23,6 +23,7 @@
   "from": "Ettől",
   "to": "Eddig",
   "clearDates": "dátumok törlése",
+  "reshuffle": "Újrakeverés",
   "widget": {
     "show": "Megjelenítés",
     "sort": "Rendezés",

frontend/src/lib/api.ts

@@ -73,6 +73,9 @@ export interface FeedFilters {
   tagMode: "or" | "and";
   q: string;
   sort: string;
+  // Re-roll token for the "shuffle" sort; bumped by the reshuffle button so the
+  // feed re-queries with a fresh order. Ignored by every other sort.
+  seed?: number;
   includeNormal: boolean;
   includeShorts: boolean;
   includeLive: boolean;
@@ -153,6 +156,7 @@ function feedQuery(f: FeedFilters, offset: number, limit: number): string {
   p.set("tag_mode", f.tagMode);
   if (f.q) p.set("q", f.q);
   p.set("sort", f.sort);
+  if (f.sort === "shuffle" && f.seed) p.set("seed", String(f.seed));
   p.set("show_normal", String(f.includeNormal));
   p.set("include_shorts", String(f.includeShorts));
   p.set("include_live", String(f.includeLive));