feat(TrainingGroup): add excludeFromQuickDiaryCreate feature and update related logic

- Introduced a new boolean field `excludeFromQuickDiaryCreate` in the TrainingGroup model to control group visibility in quick diary creation.
- Updated the `updateTrainingGroup` service method to handle the new field, allowing for dynamic updates based on user input.
- Enhanced the TrainingTimesTab component to include a checkbox for excluding groups from quick diary creation, improving user interaction.
- Updated localization files to include new strings related to the exclude feature, ensuring clarity in multiple languages.
- Refactored logic in DiaryView and mobile app to consider the new exclusion criteria when suggesting training slots.

backend/migrations/20260514_add_exclude_from_quick_diary_create_to_training_group.sql

@@ -0,0 +1,4 @@
+-- Trainingsgruppen vom Tagebuch-Schnellanlegen ausnehmen (optional)
+ALTER TABLE training_group
+ADD COLUMN exclude_from_quick_diary_create TINYINT(1) NOT NULL DEFAULT 0
+COMMENT '1 = Gruppe bei Schnellanlegen-Terminsuche ignorieren';