feat(settings): add Reset to Default button

[bxn-dev]

Fixes: #102

Adds a "Reset to Default" button in the Settings modal. Resets all
settings to their default values via a new app_get_default_settings
Tauri command.

• Tauri command app_get_default_settings returning Settings::default()
• Frontend api.app.getDefaultSettings() method
• Reset button visible when current settings differ from defaults
• Native confirm dialog via @tauri-apps/plugin-dialog before resetting
• Form updated in-place, modal stays open after reset

[Kenya-DK]

can y do so the "Reset all settings to default values?" can be translatede too

[bxn-dev]

@Kenya-DK while doing i noticed, that we just have 3 language files for like 15 languages, i could add a few or atleast a german one, since i am a german

[Kenya-DK]

Sure as long y do it in a new PR

[bxn-dev]

Sure thing

[bxn-dev]

@Kenya-DK okay the dialog is translated now

[bxn-dev]

@Kenya-DK is that solution fine for you or do i need to change something else?