[App] Add onboarding wizard (#7064)

* [App] Add onboarding wizard

Took 10 minutes

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Took 7 minutes

* Adjust CI

Took 14 minutes

Took 56 seconds

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* Adjust CI again

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* Comments and fixes

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* Rebase.

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* Comments.

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* CI lol

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* CI again lol

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* Drop some settings, add some new ones.

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* Resize when expanding section

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Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/interface/widgets/onboarding/step_indicator_widget.h

@@ -0,0 +1,34 @@
+#ifndef STEP_INDICATOR_WIDGET_H
+#define STEP_INDICATOR_WIDGET_H
+
+#include <QWidget>
+
+/** @brief Row of dots showing progress through a fixed-length sequence of steps,
+ *         in the style of a mobile/OS setup flow. Purely presentational. */
+class StepIndicatorWidget : public QWidget
+{
+    Q_OBJECT
+
+public:
+    explicit StepIndicatorWidget(QWidget *parent = nullptr);
+
+    void setStepCount(int count);
+    void setCurrentStep(int index);
+
+    QSize sizeHint() const override;
+    QSize minimumSizeHint() const override;
+
+protected:
+    void paintEvent(QPaintEvent *event) override;
+
+private:
+    int stepCount = 0;
+    int currentStep = 0;
+
+    static constexpr int kDotDiameter = 8;
+    static constexpr int kActiveDotWidth = 22;
+    static constexpr int kDotSpacing = 10;
+    static constexpr int kVerticalMargin = 6;
+};
+
+#endif // STEP_INDICATOR_WIDGET_H