Apply bike resistance gain to FTMS target-resistance-level writes

Fixes resistance mismatch on bikes like the Toputure TEB5, which
internally amplifies the received resistance level (~25% higher than
requested). The FTMS_SET_INDOOR_BIKE_SIMULATION_PARAMS branch already
applied bike_resistance_gain_f/offset, but the FTMS_SET_TARGET_RESISTANCE_LEVEL
branch used by TEB5 sent the raw value. Default gain is 1.0, so this
is a no-op for anyone not configuring it.

Fixes discussion #4793

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: cagnulein

src/devices/ftmsbike/ftmsbike.cpp

@@ -356,6 +356,7 @@ void ftmsbike::forceResistance(resistance_t requestResistance) {
             uint8_t write[] = {FTMS_SET_TARGET_RESISTANCE_LEVEL, 0x00};
             if(_3G_Cardio_RB || SL010)
                 requestResistance = requestResistance * 10;
+            requestResistance = (resistance_t)qRound(((double)requestResistance) * bikeResistanceGain);
             write[1] = ((uint8_t)(requestResistance));
             writeCharacteristic(write, sizeof(write),
                                 QStringLiteral("forceResistance ") + QString::number(requestResistance));