feat(app): first-boot eager backfill for tokenized_korean_text

V007 → V009 업그레이드 시 기존 chunks 의 tokenized_korean_text 가
NULL — 첫 App::open_with_config 호출 시 자동으로 lindera ko-dic
으로 분해 후 UPDATE. chunks_au trigger 가 chunks_fts 를 자동 재-index.
사용자 재-ingest 불필요.

- crates/kebab-store-sqlite/src/store.rs:
  backfill_tokenized_korean_text(progress_cb, tokenize) API. 1000 row 마다
  commit + progress 콜백. idempotent (IS NULL 필터로 partial
  completion 재실행 안전). tokenizer 를 파라미터로 받아 §8 dep 경계 유지.
- crates/kebab-app/src/app.rs::open_with_config: run_migrations 직후
  backfill 호출. 실패 시 warn log 만 (App open 은 성공 — vector/hybrid
  mode 계속 가능). 500 row 마다 info log progress.
- crates/kebab-store-sqlite/tests/fts.rs:
  backfill_tokenized_korean_text_populates_nullable_rows 단위 test
  (idempotency 포함).
- clippy pre-existing 오류 수정 (redundant_closure, map_unwrap_or,
  cast_lossless, uninlined_format_args — kebab-app/ingest_log.rs,
  pdf_ocr_apply.rs, app.rs, tests/ocr_inspect_smoke.rs).

Spec: docs/superpowers/specs/2026-05-28-v0.20.x-korean-morphological-tokenizer-spec.md §8.1, §8.2
Plan: docs/superpowers/plans/2026-05-28-v0.20.x-korean-morphological-tokenizer-plan.md (S4)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/kebab-app/tests/ocr_inspect_smoke.rs

@@ -15,14 +15,14 @@ fn seed_ocr_events(env: &TestEnv, store: &SqliteStore) {
         store
             .record_pdf_ocr_event(
                 "run-aaa",
-                &format!("2026-05-28T0{}:00:00Z", i),
+                &format!("2026-05-28T0{i}:00:00Z"),
                 Some("doc-abc"),
                 "path/scanned.pdf",
                 i + 1,
                 Some(50_000),
                 Some(200),
                 Some(150),
-                100 + (i as u64) * 20,
+                100 + u64::from(i) * 20,
                 42,
                 true,
                 None,