feat(server/devices): users.max_devices_override 单用户设备上限覆盖(NULL走套餐默认)+ 迁移000025

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01P9G7E3wmAYL9KeYCVZVsqu

server/internal/devices/store.go

@@ -299,6 +299,26 @@ func (s *Store) GetFreePlan(ctx context.Context) (Plan, error) {
 	return p, nil
 }
 
+// GetMaxDevicesOverride returns the per-user device-cap override set by
+// migration 000025 (users.max_devices_override). NULL or <=0 means "no
+// override" (ok=false) — the caller should fall back to the plan-derived cap.
+// A positive value always wins, even if it is *smaller* than the plan's cap,
+// so operators can also tighten a specific account.
+func (s *Store) GetMaxDevicesOverride(ctx context.Context, userID int64) (int, bool, error) {
+	var override sql.NullInt64
+	row := s.db.QueryRowContext(ctx, `SELECT max_devices_override FROM users WHERE id=?`, userID)
+	if err := row.Scan(&override); err != nil {
+		if err == sql.ErrNoRows {
+			return 0, false, nil
+		}
+		return 0, false, fmt.Errorf("store.GetMaxDevicesOverride: %w", err)
+	}
+	if !override.Valid || override.Int64 <= 0 {
+		return 0, false, nil
+	}
+	return int(override.Int64), true, nil
+}
+
 // --------------------------------------------------------------------------
 // Audit log
 // --------------------------------------------------------------------------