Add german localization and fix minor typos

[gboeer]

This fixes some typos in the UI and adds a german translation for UI text elements.

Summary by Sourcery

Improve localization and fix grammatical typos in UI text

New Features:

• Added German localization file

Bug Fixes:

• Corrected grammatical errors in UI text prompts

[sourcery-ai[bot]]

Reviewer's Guide

This pull request introduces German localization by adding a de.json translation file and corrects several minor typos in the user interface text within modules/ui.py.

File-Level Changes

Change	Details	Files
Corrected minor typographical errors in UI text.	Changed 'Atleast' to 'At least' in a status message. Corrected 'select an source image' to 'select a source image' in multiple dialog titles. Corrected 'select an target image or video' to 'select a target image or video' in a dialog title. Corrected 'select an target image' to 'select a target image' in a dialog title.	modules/ui.py
Added German localization.	Introduced a new JSON file containing German translations for UI elements.	locales/de.json

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