feat(search): add baseBookOnly filter and ancestorCategoryIds indexing

[kdroidFilter]

Summary

• Add ancestorCategoryIds to Lucene index for instant category filtering
• Add baseBookOnly parameter to openSession() and computeFacets()
• Filter by is_base_book directly in Lucene instead of fetching all base book IDs
• Add getAncestorCategoryIds() to SeforimRepository

Changes

• SearchEngine.kt: Added baseBookOnly parameter to interface methods
• LuceneSearchEngine.kt: Implemented is_base_book filter in buildSearchContext()
• TextIndexWriter.kt: Added ancestorCategoryIds parameter
• LuceneTextIndexWriter.kt: Store ancestor IDs as IntPoints and StoredField
• BuildLuceneIndex.kt: Pre-compute and index ancestor category IDs per line
• SeforimRepository.kt: Added getAncestorCategoryIds() method

Benefits

• Instant filtering by base books (no DB query for all base book IDs)
• Instant category filtering via pre-indexed ancestors
• More efficient facet computation