Seeding nodes lease first, connect for the lease, close when idle

A failed NNTP login gives the range back uncounted (no attempt used), and a
node with nothing to lease holds no connection. Replaces log-in-before-lease,
which kept idle connections and logged in again every minute while idle.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/services/SeedOrchestrator.ts

@@ -97,13 +97,18 @@ class SeedOrchestrator {
     await db.from('seed_ranges').where('id', rangeId).update({ status: 'done', done_at: new Date(), heartbeat_at: new Date(), error: null })
   }
 
-  /** A node gives a range back (it failed, or is shutting down); it's queued again unless it failed too often. */
-  async release(nodeId: number, rangeId: number, error?: string) {
+  /**
+   * A node gives a range back (it failed, or is shutting down); it's queued
+   * again unless it failed too often. `uncounted`: the node never started on
+   * it (couldn't reach its news server), so the lease doesn't count as an attempt.
+   */
+  async release(nodeId: number, rangeId: number, error?: string, uncounted = false) {
     const range = await this.leased(nodeId, rangeId)
+    const attempts = uncounted ? Math.max(0, range.attempts - 1) : range.attempts
     await db
       .from('seed_ranges')
       .where('id', rangeId)
-      .update({ status: range.attempts >= MAX_ATTEMPTS ? 'failed' : 'queued', node_id: null, error: error?.slice(0, 2000) ?? null })
+      .update({ status: attempts >= MAX_ATTEMPTS ? 'failed' : 'queued', node_id: null, attempts, error: error?.slice(0, 2000) ?? null })
   }
 
   private async leased(nodeId: number, rangeId: number) {