feat(transcription): add "Alle als fertig markieren" bulk action (#345) (#352)

## Summary

Implements the bulk "Alle als fertig markieren" action for the transcription panel requested in #345.

### Backend

- Added `PUT /api/documents/{documentId}/transcription-blocks/review-all` endpoint to `TranscriptionBlockController`, guarded with `@RequirePermission(Permission.WRITE_ALL)`
- Added `markAllBlocksReviewed(UUID documentId, UUID userId)` to `TranscriptionService` — `@Transactional`, single DB round-trip via `blockRepository.saveAll()`, emits one `BLOCK_REVIEWED` audit event per previously-unreviewed block
- Returns full updated block list (same shape as `listBlocks`) for a clean frontend update pass
- 5 new `TranscriptionServiceTest` unit tests (idempotency, audit events, empty document)
- 5 new `TranscriptionBlockControllerTest` `@WebMvcTest` tests (401, 403, 200 happy path, 200 empty, 401 user not found)
- All 68 backend tests pass

### Frontend

- Added `onMarkAllReviewed?: () => Promise<void>` prop to `TranscriptionEditView` (optional, consistent with `onTriggerOcr` pattern)
- Button placed in sticky progress header, right-aligned next to `reviewedCount / totalCount geprüft`
- Button is **disabled** (not hidden) when all blocks are already reviewed — `title="Alle Blöcke sind bereits als fertig markiert"` (Decision 1)
- Loading spinner replaces checkmark icon during operation — always shown (Decision 4, no threshold)
- Handler `markAllReviewed()` added to `documents/[id]/+page.svelte`, wired as `onMarkAllReviewed`
- 5 new `TranscriptionEditView.svelte.spec.ts` Vitest Browser component tests; all 25 tests pass

### Decisions applied

| # | Question | Choice |
|---|---|---|
| 1 | Button when all reviewed | **Disabled** with `title` tooltip |
| 2 | Audit log | **N individual BLOCK_REVIEWED events** (one per unreviewed block) |
| 3 | Atomicity | **All-or-nothing** via `@Transactional` |
| 4 | Loading indicator | **Always show** during operation |

Closes #345

Co-authored-by: Marcel <marcel@familienarchiv>
Reviewed-on: http://heim-nas:3005/marcel/familienarchiv/pulls/352

backend/api_tests/Transcription.http

@@ -0,0 +1,3 @@
+### Mark all blocks as reviewed
+PUT http://localhost:8080/api/documents/{{documentId}}/transcription-blocks/review-all
+Authorization: Basic admin admin123