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/api/src/db/schema.ts

@@ -80,6 +80,8 @@ export const connections = pgTable(
     status: text('status').$type<'active' | 'error'>().notNull().default('active'),
     lastError: text('last_error'),
     lastPolledAt: timestamp('last_polled_at', { withTimezone: true }),
+    /** Last time this connection reported something playing; used to spot links that silently broke. */
+    lastActivityAt: timestamp('last_activity_at', { withTimezone: true }),
     /** Provider-specific state, e.g. Jellyfin server URL or discovered Plex servers. */
     meta: jsonb('meta').$type<Record<string, unknown>>().notNull().default({}),
     /** Secret path segment for inbound webhooks (/webhooks/:provider/:secret). */
@@ -138,6 +140,8 @@ export const nowPlaying = pgTable(
     source: text('source').$type<NowPlayingProvider>().notNull(),
     /** App name when a phone reported it, e.g. "Spotify". */
     sourceApp: text('source_app'),
+    /** Where the data came from, for attribution (e.g. the user's Last.fm profile). */
+    sourceUrl: text('source_url'),
     isPlaying: boolean('is_playing').notNull(),
     progressMs: integer('progress_ms'),
     startedAt: timestamp('started_at', { withTimezone: true }).notNull().defaultNow(),