feat: two-phase indexation with direct thumbnail generation in indexer

Phase 1 (discovery): walkdir + filename-only metadata, zero archive I/O.
Books are visible immediately in the UI while Phase 2 runs in background.

Phase 2 (analysis): open each archive once via analyze_book() to extract
page_count and first page bytes, then generate WebP thumbnail directly in
the indexer — removing the HTTP roundtrip to the API checkup endpoint.

- Add parse_metadata_fast() (infallible, no archive I/O)
- Add analyze_book() returning (page_count, first_page_bytes) in one pass
- Add looks_like_image() magic bytes check for unrar p stdout validation
- Add lsar fallback in list_cbr_images() for UTF-16BE encoded filenames
- Add directory_mtimes table to skip unchanged dirs on incremental scans
- Add analyzer.rs: generate_thumbnail, analyze_library_books, regenerate_thumbnails
- Remove run_checkup() from API; indexer handles thumbnail jobs directly
- Remove api_base_url/api_bootstrap_token from IndexerConfig and AppState
- Add unar + poppler-utils to indexer Dockerfile
- Fix smoke.sh: wait for job completion, check thumbnail_url field

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

AGENTS.md

@@ -251,9 +251,10 @@ stripstream-librarian/
 |------|---------|
 | `apps/api/src/books.rs` | Book CRUD endpoints |
 | `apps/api/src/pages.rs` | Page rendering & caching (LRU + disk) |
-| `apps/api/src/thumbnails.rs` | Thumbnail generation (triggered by indexer) |
+| `apps/api/src/thumbnails.rs` | Endpoints pour créer des jobs thumbnail (rebuild/regenerate) |
 | `apps/api/src/state.rs` | AppState, Semaphore concurrent_renders |
-| `apps/indexer/src/scanner.rs` | Filesystem scan, rayon parallel parsing |
+| `apps/indexer/src/scanner.rs` | Phase 1 discovery : scan rapide sans I/O archive, skip dossiers inchangés |
+| `apps/indexer/src/analyzer.rs` | Phase 2 analysis : `analyze_book` + génération thumbnails WebP |
 | `apps/indexer/src/batch.rs` | Bulk DB ops via UNNEST |
 | `apps/indexer/src/worker.rs` | Job loop, watcher, scheduler orchestration |
 | `crates/parsers/src/lib.rs` | Format detection, metadata parsing |
@@ -302,5 +303,5 @@ fn remap_libraries_path(path: &str) -> String {
 - **Dependencies**: External crates are defined in workspace `Cargo.toml`, not individual `Cargo.toml`.
 - **Database**: PostgreSQL is required. Run migrations before starting services.
 - **External Tools**: 4 system tools required — `unrar` (CBR page count), `unar` (CBR extraction), `pdfinfo` (PDF page count), `pdftoppm` (PDF page render). Note: `unrar` and `unar` are distinct tools.
-- **Thumbnails**: generated by the **API** service (not the indexer). The indexer triggers a checkup via `POST /index/jobs/:id/thumbnails/checkup` after indexing.
+- **Thumbnails**: generated by the **indexer** service (phase 2, `analyzer.rs`). The API only creates jobs in DB — it does not generate thumbnails directly.
 - **Sub-AGENTS.md**: module-specific guidelines in `apps/api/`, `apps/indexer/`, `apps/backoffice/`, `crates/parsers/`.