fix: Corregge calcolo PV_in_watts in modalità QPGS parallela

DATA[25] ('PV Input Current') nei reply QPGS è in realtà la corrente
in uscita dal SCC (Solar Charge Controller) verso la batteria, a tensione
batteria - NON la corrente ai pannelli PV a tensione PV.

Bug: PV_WATTS = DATA[14] (PV voltage ~246V) * DATA[25] (SCC current ~55A)
     → valore ~4-5x troppo alto (es. 246.8 * 55 = 13574W per inverter)

Fix: PV_WATTS = DATA[11] (battery voltage ~54V) * DATA[25] (SCC current)
     → valore corretto (es. 53.9 * 55 = 2964W per inverter)

Identico al comportamento di QPIGS in main.cpp:
  pv_input_watts = scc_voltage * pv_input_current
  con commento: 'input current is going to battery at battery voltage
  (NOT at PV voltage)'

sources/inverter-mqtt/mqtt-push-parallel.sh

@@ -514,9 +514,13 @@ for idx in "${!VALID_SERIALS[@]}"; do
         [ "${DATA[14]}" ] && pushMQTTData "$inv_id" "PV_in_voltage" "${DATA[14]}"
         [ "${DATA[25]}" ] && pushMQTTData "$inv_id" "PV_in_current" "${DATA[25]}"
         
-        # Calculate PV watts (V * A)
-        if [ ! -z "${DATA[14]}" ] && [ ! -z "${DATA[25]}" ]; then
-            PV_WATTS=`echo "${DATA[14]} ${DATA[25]}" | awk '{printf "%.1f", $1 * $2}'`
+        # Calculate PV watts using battery voltage (DATA[11]) * SCC output current (DATA[25]).
+        # NOTE: Like QPIGS, DATA[25] ("PV Input Current") is actually the current going to the
+        # battery FROM the solar charge controller at battery voltage (NOT at PV panel voltage).
+        # Using PV voltage (DATA[14]) here would give a value ~4-5x too high.
+        # This mirrors the QPIGS formula: pv_input_watts = scc_voltage * pv_input_current
+        if [ ! -z "${DATA[11]}" ] && [ ! -z "${DATA[25]}" ]; then
+            PV_WATTS=`echo "${DATA[11]} ${DATA[25]}" | awk '{printf "%.1f", $1 * $2}'`
             pushMQTTData "$inv_id" "PV_in_watts" "$PV_WATTS"
         fi