Fix case-sensitive flight mode comparisons

Fixed a bug where the "Start mission" action failed on ArduPilot,
displaying an error popup with the message "Unable to start mission:
Vehicle failed to change to Auto mode." The issue was caused by
case-sensitive comparisons between flight mode strings from the vehicle
and the reference strings. Moving away from using strings entirely
should be considered.

Replaced direct string comparisons with case-insensitive comparisons
using QString::compare() with Qt::CaseInsensitive flag. This fix
resolves the immediate issue and also corrects a few other incorrect
mode comparisons unrelated to the "Start mission" problem.

src/AutoPilotPlugins/APM/APMSubMotorComponentController.cc

@@ -22,7 +22,7 @@ void APMSubMotorComponentController::handleNewMessages(int uasid, int componenti
     Q_UNUSED(uasid);
     Q_UNUSED(componentid);
     Q_UNUSED(severity);
-    if (_vehicle->flightMode() == "Motor Detection"
+    if (QString::compare(_vehicle->flightMode(), "Motor Detection", Qt::CaseInsensitive) == 0
         && (text.toLower().contains("thruster") || text.toLower().contains("motor"))) {
         _motorDetectionMessages += text + QStringLiteral("\n");
         emit motorDetectionMessagesChanged();

src/FirmwarePlugin/APM/APMFirmwarePlugin.cc

@@ -670,7 +670,7 @@ const QVariantList& APMFirmwarePlugin::toolIndicators(const Vehicle* vehicle)
 
 bool APMFirmwarePlugin::isGuidedMode(const Vehicle* vehicle) const
 {
-    return vehicle->flightMode() == "Guided";
+    return QString::compare(vehicle->flightMode(), "Guided", Qt::CaseInsensitive) == 0;
 }
 
 void APMFirmwarePlugin::_soloVideoHandshake(void)

src/FirmwarePlugin/FirmwarePlugin.cc

@@ -365,7 +365,7 @@ bool FirmwarePlugin::_armVehicleAndValidate(Vehicle* vehicle)
 
 bool FirmwarePlugin::_setFlightModeAndValidate(Vehicle* vehicle, const QString& flightMode)
 {
-    if (vehicle->flightMode() == flightMode) {
+    if (QString::compare(vehicle->flightMode(), flightMode, Qt::CaseInsensitive) == 0) {
         return true;
     }
 
@@ -377,7 +377,7 @@ bool FirmwarePlugin::_setFlightModeAndValidate(Vehicle* vehicle, const QString&
 
         // Wait for vehicle to return flight mode
         for (int i=0; i<13; i++) {
-            if (vehicle->flightMode() == flightMode) {
+            if (QString::compare(vehicle->flightMode(), flightMode, Qt::CaseInsensitive) == 0) {
                 flightModeChanged = true;
                 break;
             }

src/Vehicle/StandardModes.cc

@@ -175,7 +175,7 @@ QString StandardModes::flightMode(uint32_t custom_mode) const
 bool StandardModes::setFlightMode(const QString &flightMode, uint32_t *custom_mode)
 {
     for (auto iter = _modes.constBegin(); iter != _modes.constEnd(); ++iter) {
-        if (iter->name == flightMode) {
+        if (QString::compare(iter->name, flightMode, Qt::CaseInsensitive) == 0) {
             *custom_mode = iter.key();
             return true;
         }