add related hashtag pruning to maintenance worker

src/worker/index.ts

@@ -304,6 +304,23 @@ const maintenanceWorker = new Worker(
     console.log(
       `[maintenance] pruned snapshots — fund NAV: ${deletedFundNav.count} rows, user portfolio: ${deletedUserPortfolio.count} rows (>7d)`,
     )
+
+    // ── Related hashtag pruning ────────────────────────────────────────────
+    // 1. Null-target records: the related hashtag was deleted (onDelete: SetNull)
+    //    or was never tracked. Delete unconditionally — the upsert in the price
+    //    worker will recreate them if the co-occurrence is seen again.
+    // 2. Weak associations: low co-occurrence records that were never reinforced,
+    //    pruned after 30 days of inactivity.
+    const relatedCutoff = new Date(now.getTime() - 30 * 24 * 60 * 60 * 1000)
+    const [deletedNullTarget, deletedWeak] = await Promise.all([
+      prisma.relatedHashtag.deleteMany({ where: { relatedId: null } }),
+      prisma.relatedHashtag.deleteMany({
+        where: { relatedId: { not: null }, coOccurrences: { lt: 5 }, updatedAt: { lt: relatedCutoff } },
+      }),
+    ])
+    console.log(
+      `[maintenance] pruned relatedHashtag — ${deletedNullTarget.count} null-target, ${deletedWeak.count} weak (>30d, <5 co-occurrences)`,
+    )
   },
   { connection: redisOpts() },
 )