feat: Onboarding-Seite bei leerem Dashboard + Info-Sektion in Settings

[BEKO2210]

Dashboard (wenn keine Produkte vorhanden):

• Begrüßungsbildschirm mit PrepTrack-Logo und Titel
• Drei Schnellstart-Buttons: Barcode scannen, Manuell erfassen, Backup importieren
• Import direkt vom Dashboard mit Bildlade-Fortschrittsbalken
• Feature-Übersicht mit allen Kernfunktionen

Settings:

• Neue aufklappbare "Funktionen"-Sektion mit Feature-Liste
• Icons für jede Funktion (Offline, Kamera, Bilder, Benachrichtigungen, Export, Datenschutz)

Übersetzungen für alle 6 Sprachen (de, en, pt, ar, it, fr) hinzugefügt.

https://claude.ai/code/session_015qtYL5oNDLJYrmH5JRAGqS

Description

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• CI/CD changes

Related Issues

Screenshots

Before	After

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• All UI text is in German with correct umlauts (or uses i18n keys)
• I have added translation keys for both de and en if new text was added
• npm run build completes without errors
• npm run test passes all tests
• npx tsc --noEmit reports no type errors
• No unused imports or variables (noUnusedLocals: true)
• Tailwind classes used (no separate CSS files)
• Lucide React icons used (no other icon libraries)

Testing

• Tested in Chrome
• Tested in Firefox/Safari
• Tested on mobile
• Tested offline functionality
• Tested dark mode
• Tested light mode