Add GET /library/scan/batch endpoint to list batch jobs

[jakebromberg]

Summary

Add a paginated endpoint for listing a user's batch scan jobs. This supports the HistoryView in the library-scanner iOS app, which needs to display past batch jobs without fetching full results for each one.

Changes

Service (apps/backend/services/scanner/batch.ts)

• Add BatchJobSummary and PaginatedJobList interfaces
• Add listJobs(userId, limit, offset) function that queries scan_jobs with WHERE user_id = ?, ordered by created_at DESC, with LIMIT/OFFSET pagination and total count

Controller (apps/backend/controllers/scanner.controller.ts)

• Add listBatchJobs handler that parses limit (default 20, max 100) and offset (default 0) from query params

Routes (apps/backend/routes/scanner.route.ts)

• Add GET /batch route before the :jobId route (Express matches first), requiring catalog: read permission

Tests

7 new tests:

• Service: empty result, sorted order, limit/offset params, field mapping (4 tests)
• Controller: 200 response, default pagination, limit clamping (3 tests)

Related

• Targets feature/scanner-batch-processing (PR Add batch scan processing endpoints #215)
• iOS consumer: WXYC/library-scanner HistoryView