Implement 'agc' reset for SX126x & LR11x0 chip families (#9705)

* Implement 'agc' reset for SX126x chip family

There's no actual agc on SX126x chips but you can reset the analog
registers by doing a warm sleep & running calibration.

* Address PR comments & implement for LR11x0 too

* calibrate for configured frequency band

* Gate LR11X0_AGC_RESET

src/main.cpp

@@ -1125,6 +1125,13 @@ void loop()
             lastRadioMissedIrqPoll = millis();
             RadioLibInterface::instance->pollMissedIrqs();
         }
+
+        // Periodic AGC reset — warm sleep + recalibrate to prevent stuck AGC gain
+        static uint32_t lastAgcReset;
+        if (!Throttle::isWithinTimespanMs(lastAgcReset, AGC_RESET_INTERVAL_MS)) {
+            lastAgcReset = millis();
+            RadioLibInterface::instance->resetAGC();
+        }
     }
 
 #ifdef DEBUG_STACK