music: Last.fm-style stats with 7d/30d/1y/all ranges and genres

- Range picker (?range=7d|30d|1y|all) drives every section; the hours chart
  covers the whole range (daily for 7d/30d, weekly for 1y, monthly for all).
- Genres from Last.fm artist top tags (music.artist_tags, normalised and
  filtered), split by artist listening time, with a per-bucket stacked chart.
- Listening clock, new artists, comparison with the previous period and top
  movers, streaks, milestones, top albums with art, rank changes.
- music.play_facts materialized view (refreshed by the app when plays arrive)
  plus a per-range cache keep the page fast.
- scripts/music-fetch-tags.ts backfills tags, most-played artists first.

scripts/music-fetch-tags.ts

@@ -0,0 +1,85 @@
+// Fetch Last.fm artist top tags into music.artist_tags (genres for /trackers/music).
+//
+//   LASTFM_API_KEY=... bun scripts/music-fetch-tags.ts [--limit N] [--sleep 250] [--refetch-days 90]
+//
+// Most-played artists first (all time). Artists fetched within --refetch-days are skipped
+// ('not_found' is retried after 30 days), so a re-run only picks up new artists. Tags are
+// normalised and filtered (src/lib/music/tags.ts); the top 5 genres per artist are kept.
+// Rate limit: one request per --sleep ms (Last.fm asks for at most 5/s), back-off on 429/5xx.
+import { pickTags } from '../src/lib/music/tags';
+import { arg, musicDb, sleep } from './music-db';
+
+const apiKey = process.env.LASTFM_API_KEY;
+if (!apiKey) throw new Error('Set LASTFM_API_KEY');
+const limit = Number(arg('limit') ?? 100_000);
+const pause = Number(arg('sleep') ?? 250);
+const refetchDays = Number(arg('refetch-days') ?? 90);
+
+type LastfmTags = { toptags?: { tag?: { name: string; count: number }[] }; error?: number };
+
+async function topTags(name: string): Promise<LastfmTags> {
+	const url = `https://ws.audioscrobbler.com/2.0/?${new URLSearchParams({
+		method: 'artist.gettoptags',
+		artist: name,
+		autocorrect: '1',
+		api_key: apiKey!,
+		format: 'json'
+	})}`;
+	for (let attempt = 0; ; attempt++) {
+		const response = await fetch(url, { signal: AbortSignal.timeout(15_000) }).catch(() => null);
+		const json = response ? ((await response.json().catch(() => ({}))) as LastfmTags) : {};
+		const retry =
+			!response ||
+			response.status === 429 ||
+			response.status >= 500 ||
+			json.error === 29 ||
+			json.error === 8 ||
+			json.error === 11 ||
+			json.error === 16;
+		if (!retry || attempt >= 4) return json;
+		await sleep(2_000 * 2 ** attempt);
+	}
+}
+
+const sql = musicDb();
+try {
+	const artists = await sql`
+		select a.id, a.name, count(*)::int as plays
+		from music.plays p join music.tracks t on t.id = p.track_id
+		join music.artists a on a.id = t.artist_id
+		left join music.artist_tag_fetch tf on tf.artist_id = a.id
+		where tf.artist_id is null
+		   or (tf.status = 'ok' and tf.fetched_at < now() - make_interval(days => ${refetchDays}))
+		   or tf.status like 'error%'
+		   or (tf.status <> 'ok' and tf.fetched_at < now() - interval '30 days')
+		group by a.id order by plays desc, a.id limit ${limit}`;
+	console.log(`${artists.length} artists to fetch.`);
+	let tagged = 0;
+	for (const [i, artist] of artists.entries()) {
+		const json = await topTags(artist.name as string);
+		const tags = pickTags(json.toptags?.tag ?? []);
+		const status =
+			json.error === 6
+				? 'not_found'
+				: json.error
+					? `error ${json.error}`
+					: tags.length
+						? 'ok'
+						: 'no_tags';
+		await sql.begin(async (tx) => {
+			if (!json.error || json.error === 6) {
+				await tx`delete from music.artist_tags where artist_id = ${artist.id}`;
+				for (const t of tags)
+					await tx`insert into music.artist_tags (artist_id, tag, weight) values (${artist.id}, ${t.tag}, ${t.weight})`;
+			}
+			await tx`insert into music.artist_tag_fetch (artist_id, status) values (${artist.id}, ${status})
+				on conflict (artist_id) do update set status = excluded.status, fetched_at = now()`;
+		});
+		if (tags.length) tagged++;
+		if ((i + 1) % 250 === 0) console.log(`  ${i + 1}/${artists.length} (${tagged} with genres)`);
+		await sleep(pause);
+	}
+	console.log(`Done: ${tagged} of ${artists.length} artists got genres.`);
+} finally {
+	await sql.end();
+}