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/web/Dockerfile

@@ -18,7 +18,9 @@ COPY --from=prepare /app/tsconfig.base.json ./tsconfig.base.json
 # NEXT_PUBLIC_* values are inlined into the browser bundle at build time,
 # so the API URL is a build argument, not a runtime setting.
 ARG NEXT_PUBLIC_API_URL=http://localhost:4000
+ARG NEXT_PUBLIC_DONATION_URL=
 ENV NEXT_PUBLIC_API_URL=$NEXT_PUBLIC_API_URL \
+    NEXT_PUBLIC_DONATION_URL=$NEXT_PUBLIC_DONATION_URL \
     NEXT_TELEMETRY_DISABLED=1
 RUN npx turbo run build --filter=@musicshare/web