fix: upsert publisher row on torrent ingest, backfill migration

insert_torrent now upserts into publishers so torrent authors appear
in the publishers table immediately, making the name/nip05 join work
on the indexed and dashboard pages. Migration 006 backfills existing
torrent pubkeys on fresh DB opens.

src/db/migrations/006_backfill_publishers.sql

@@ -0,0 +1,9 @@
+-- Backfill publishers table from existing torrent pubkeys.
+-- Safe to run on databases that already have publisher rows (ON CONFLICT is a no-op for those).
+INSERT INTO publishers (pubkey, torrents_n, last_seen)
+SELECT pubkey, COUNT(*), MAX(ingested_at)
+FROM torrents
+GROUP BY pubkey
+ON CONFLICT(pubkey) DO UPDATE SET
+  torrents_n = MAX(publishers.torrents_n, excluded.torrents_n),
+  last_seen  = MAX(publishers.last_seen,  excluded.last_seen);

src/db/queries.rs

@@ -87,6 +87,19 @@ pub async fn insert_torrent(pool: &SqlitePool, r: &TorrentRecord) -> anyhow::Res
         return Ok(());
     }
 
+    // Ensure the publisher row exists and bump their counters
+    sqlx::query(
+        "INSERT INTO publishers (pubkey, torrents_n, last_seen)
+         VALUES (?, 1, ?)
+         ON CONFLICT(pubkey) DO UPDATE SET
+           torrents_n = torrents_n + 1,
+           last_seen  = excluded.last_seen",
+    )
+    .bind(&r.pubkey)
+    .bind(r.ingested_at)
+    .execute(&mut *tx)
+    .await?;
+
     for url in &r.trackers {
         sqlx::query("INSERT OR IGNORE INTO trackers (event_id, url) VALUES (?,?)")
             .bind(&r.event_id)