test: expand usePersonalization hook test coverage

Add comprehensive test coverage for usePersonalization hook including:
- Error handling for queries and mutations
- Mutation state tracking (pending, success states)
- findNextAvailablePosition helper function edge cases
- Advanced scenarios for combined hooks (useSavedViewsManager, usePreferencesManager, useWidgetLibrary)
- Layout operations edge cases (non-existent widgets, single column grids, property preservation)

Tests cover loading states, error boundaries, empty states, and complex
grid positioning logic. Increases overall test coverage for the
personalization feature module.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: aledlie