Add screenshots for common first-run workflows

[LuTiK1984]

Summary

Add or refresh screenshots that show the most common first-run workflows.

Suggested screenshots

• Desktop app launch.
• Tuner input device selection.
• VST3 folder layout after installation.
• DAW plugin scan result.
• Plugin opened inside a DAW.
• Logs folder location.

Output

Place images under docs/images/ and link them from README or a dedicated quick-start guide.

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Кратко

Добавить скриншоты для первых шагов пользователя: запуск Desktop, выбор входа, установка VST3, сканирование DAW, открытие плагина и папка логов.