fix(autotells): preload tell history fully up to the user-configured limit

PreloadHistory had a hardcoded 500-row SQL scan window that capped the
per-partner history pull regardless of the AutoTellTabsHistoryPreload
setting. For active users with many tell partners, the scan window
filled up with chatter from other partners and pushed less-frequent
partners' history off the back end — pinned tabs reloaded empty even
though the messages were still in the database.

Drops the hardcoded scan cap. The (Receiver, Date) index keeps SQL fast
on the now-unbounded read, and the client-side loop still breaks as
soon as the configured per-tab limit is hit, so decode cost stays
proportional to the depth at which `limit` matches accumulate (typically
shallow even for chatty users).

HellionChat/MessageStore.cs

@@ -1001,12 +1001,18 @@ internal class MessageStore : IDisposable
     // SQL narrows by Receiver + ChatType (indexed); client does the final
     // PlayerPayload comparison. sqlScanLimit caps the scan to stay within
     // the message-processing worker thread budget.
+    // Walks the full receiver-filtered tell history newest-first and stops
+    // as soon as the per-partner match count reaches `limit`. The previous
+    // hardcoded 500-row scan window cut active users' less-frequent pinned
+    // partners out of the result whenever other partners' chatter pushed
+    // them off the back of the window. Index on (Receiver, Date) keeps the
+    // SQL side cheap; the client-side break bounds the actual decode cost
+    // to roughly the depth at which `limit` partner matches accumulate.
     internal IReadOnlyList<Message> GetTellHistoryWithSender(
         ulong receiver,
         string senderName,
         uint senderWorld,
-        int limit,
-        int sqlScanLimit = 500
+        int limit
     )
     {
         if (limit <= 0)
@@ -1024,14 +1030,12 @@ internal class MessageStore : IDisposable
             WHERE deleted = false
               AND Receiver = $Receiver
               AND ChatType IN ($TellIncoming, $TellOutgoing)
-            ORDER BY Date DESC
-            LIMIT $ScanLimit;
+            ORDER BY Date DESC;
         ";
             cmd.CommandTimeout = 60;
             cmd.Parameters.AddWithValue("$Receiver", receiver);
             cmd.Parameters.AddWithValue("$TellIncoming", (int)ChatType.TellIncoming);
             cmd.Parameters.AddWithValue("$TellOutgoing", (int)ChatType.TellOutgoing);
-            cmd.Parameters.AddWithValue("$ScanLimit", sqlScanLimit);
 
             var collected = new List<Message>();
             using var enumerator = new MessageEnumerator(cmd.ExecuteReader(), _logger);