Unlock everything, add a donation link, credit Last.fm, nudge re-linking

- Every feature is free for everyone (the plan system stays for later);
  remaining limits are abuse guards
- Optional website donation link (NEXT_PUBLIC_DONATION_URL). Not shown in
  the mobile apps, where tips to the developer generally need in-app
  purchase
- Last.fm/ListenBrainz-sourced plays link to the user's profile, as
  Last.fm's API terms require
- Connections track when they last saw activity; a scrobbler silent for
  over a week prompts re-linking Spotify (its link expires every 6 months)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MzFywujuH9TiuXbr9vjoX8

apps/mobile/src/components/RelinkReminder.tsx

@@ -0,0 +1,27 @@
+import * as WebBrowser from 'expo-web-browser';
+import useSWR from 'swr';
+import { SERVICE_LABELS, SPOTIFY_LINK_PAGES, isQuietScrobbler, type ConnectionDTO } from '@musicshare/shared';
+import { Body, Button, Card } from './ui';
+
+/** Nudge when Last.fm/ListenBrainz has gone quiet: usually Spotify's 6-month link expired. */
+export function RelinkReminder() {
+  const { data: connections = [] } = useSWR<ConnectionDTO[]>('/connections');
+  const quiet = connections.find((c) => isQuietScrobbler(c));
+  if (!quiet || !isQuietScrobbler(quiet)) return null;
+  const name = SERVICE_LABELS[quiet.provider];
+  return (
+    <Card>
+      <Body>
+        Nothing new from {name} in over a week. If you listen on Spotify, its link to {name} expires every 6 months.
+        Re-link it to keep sharing.
+      </Body>
+      <Button
+        small
+        variant="primary"
+        title={`Re-link Spotify on ${name}`}
+        onPress={() => WebBrowser.openBrowserAsync(SPOTIFY_LINK_PAGES[quiet.provider])}
+        style={{ alignSelf: 'flex-start' }}
+      />
+    </Card>
+  );
+}