query_handler refactored: - Extract QueryParams struct with validation - Extract SearchMethod enum - Extract build_search_response helper - Extract apply_rbac_filter helper - Extract execute_hybrid_search helper - Complexity: 14 → 6 ingest_handler helpers: - Extract IngestParams struct with validation - Extract IngestParamsError with responses - Extract IngestResponse builder New tests (18 total): - QueryParams validation (10 tests) - IngestParams validation (8 tests) Total tests: 688 (was 670)