Show discovery progress in the top-bar indicator alongside downloads/tasks

The DownloadIndicator in Layout.jsx now queries discovery-status and shows
discovery progress the same way it shows active downloads and channel tasks:
- Spinning icon appears in the navbar when discovery is running
- Hover popover shows "Discovering channels" with X/Y count and a progress bar
- Polls every 10 s while running, 60 s when idle
- Primary label priority: download % > task phase > discovery X/Y

Discovery page header simplified: progress bar and verbose status removed
since the top-bar indicator now handles it. "Find more" button still
disables while running.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/Discovery.jsx

@@ -218,7 +218,7 @@ export default function DiscoveryPage() {
     queryKey: ["discovery-status"],
     queryFn: () => getDiscoveryStatus().then(r => r.data),
     staleTime: 10_000,
-    refetchInterval: (query) => query.state.data?.progress?.running ? 10_000 : 60_000,
+    refetchInterval: (query) => (query.state.data?.progress?.running ? 10_000 : 60_000),
   });
 
   const refreshMut = useMutation({
@@ -248,52 +248,37 @@ export default function DiscoveryPage() {
     <div className="flex flex-col gap-6">
       {/* Header */}
       <div className="flex items-center justify-between gap-4">
-        <div className="min-w-0 flex-1">
+        <div className="min-w-0">
           <h1 className="font-display font-bold text-2xl text-zinc-100">Discover</h1>
           {discStatus && (
             <p className="text-xs text-zinc-500 mt-0.5">
-              {discStatus.progress?.running
-                ? `Finding channels… ${discStatus.progress.done} / ${discStatus.progress.total}`
-                : discStatus.pending_count > 0
-                  ? `${discStatus.pending_count} channel${discStatus.pending_count !== 1 ? "s" : ""} queued`
-                  : "Queue empty"}
+              {discStatus.pending_count > 0
+                ? `${discStatus.pending_count} channel${discStatus.pending_count !== 1 ? "s" : ""} queued`
+                : "Queue empty"}
               {discStatus.last_run
                 ? ` · last refreshed ${new Date(discStatus.last_run + "Z").toLocaleDateString(undefined, { month: "short", day: "numeric", hour: "2-digit", minute: "2-digit" })}`
                 : " · never refreshed"}
             </p>
           )}
-          {discStatus?.progress?.running && (
-            <div className="mt-1.5 h-1 w-48 rounded-full bg-zinc-800 overflow-hidden">
-              <div
-                className="h-full bg-accent rounded-full transition-all duration-500"
-                style={{ width: `${Math.round((discStatus.progress.done / discStatus.progress.total) * 100)}%` }}
-              />
-            </div>
-          )}
         </div>
         <button
           onClick={() => refreshMut.mutate()}
           disabled={refreshMut.isPending || discStatus?.progress?.running}
           className="shrink-0 flex items-center gap-2 text-sm font-medium px-4 py-2 bg-zinc-800 text-zinc-300 rounded-lg hover:bg-zinc-700 transition-colors disabled:opacity-60"
         >
-          {discStatus?.progress?.running ? (
+          {refreshMut.isPending && (
             <svg className="w-3.5 h-3.5 animate-spin" fill="none" viewBox="0 0 24 24">
               <circle className="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" strokeWidth="4" />
               <path className="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8v4a4 4 0 00-4 4H4z" />
             </svg>
-          ) : refreshMut.isPending ? (
-            <svg className="w-3.5 h-3.5 animate-spin" fill="none" viewBox="0 0 24 24">
-              <circle className="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" strokeWidth="4" />
-              <path className="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8v4a4 4 0 00-4 4H4z" />
-            </svg>
-          ) : null}
+          )}
           {discStatus?.progress?.running ? "Running…" : refreshMut.isSuccess ? "Queued ✓" : refreshMut.isPending ? "Queueing…" : "Find more"}
         </button>
       </div>
 
-      {(refreshMut.isSuccess || discStatus?.progress?.running) && (
+      {refreshMut.isSuccess && !discStatus?.progress?.running && (
         <div className="px-4 py-3 rounded-xl bg-zinc-800/60 border border-zinc-700/50 text-sm text-zinc-400">
-          Discovery is running in the background — searches and channel fetches are spaced out over ~20 minutes to avoid hitting limits. New channels appear as each batch completes. Runs automatically every day.
+          Discovery is running — progress shows in the top bar. Searches are spaced out over ~20 minutes. Runs automatically every day.
         </div>
       )}