Phase 25: division leaderboard, market trade history

- Market: record buy/sell history in market_history table; expose via
  GET /market/trade-history (last 30 events, newest first)
- Division: GET /division/leaderboard returns 10-club table with 9 seeded
  NPC entries + player row, sorted by pts; stable within a season
- rand feature small_rng enabled in Cargo.toml for SmallRng use
- 3 new integration tests (leaderboard count, sort order, empty trade history)
- Core: 96 tests passing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/integration_test.rs

@@ -1850,3 +1850,50 @@ async fn test_milestones_endpoint_structure() {
     assert!(json["sbcs_completed"].is_number());
     assert!(json["total_checkins"].is_number());
 }
+
+#[tokio::test]
+async fn test_leaderboard_has_ten_clubs() {
+    let app = build_test_app().await;
+    auth(&app, "LeaderboardPlayer").await;
+
+    let (status, json) = json_get(&app, "/division/leaderboard").await;
+    assert_eq!(status, StatusCode::OK, "{json}");
+    let table = json["leaderboard"].as_array().unwrap();
+    assert_eq!(table.len(), 10, "leaderboard should have 10 clubs (9 NPC + player)");
+
+    // Exactly one entry should be the player's club
+    let player_entries: Vec<_> = table.iter().filter(|e| e["is_player"].as_bool() == Some(true)).collect();
+    assert_eq!(player_entries.len(), 1, "exactly one player club entry");
+    assert!(json["division"].is_number());
+}
+
+#[tokio::test]
+async fn test_leaderboard_sorted_by_pts() {
+    let app = build_test_app().await;
+    auth(&app, "SortedLeader").await;
+
+    let (_, json) = json_get(&app, "/division/leaderboard").await;
+    let table = json["leaderboard"].as_array().unwrap();
+    let pts: Vec<i64> = table.iter().map(|e| e["pts"].as_i64().unwrap_or(0)).collect();
+    let sorted = {
+        let mut s = pts.clone();
+        s.sort_by(|a, b| b.cmp(a));
+        s
+    };
+    assert_eq!(pts, sorted, "leaderboard should be sorted by pts desc");
+    // Positions should be sequential
+    for (i, entry) in table.iter().enumerate() {
+        assert_eq!(entry["position"].as_i64().unwrap_or(-1), (i + 1) as i64);
+    }
+}
+
+#[tokio::test]
+async fn test_trade_history_empty_initially() {
+    let app = build_test_app().await;
+    auth(&app, "TradeHistPlayer").await;
+
+    let (status, json) = json_get(&app, "/market/trade-history").await;
+    assert_eq!(status, StatusCode::OK, "{json}");
+    assert!(json["trades"].is_array());
+    assert_eq!(json["trades"].as_array().unwrap().len(), 0);
+}