Add an asynchronous background job manager

[sodejm]

Title: Add an asynchronous background job manager
Type: Architecture
Estimated Size: Large
Description: Introduce a job manager that executes existing blocking GEDCOM, RootsMagic, database, OCR, and provider operations outside the prompt event loop, initially using bounded worker threads where necessary. Track job IDs, state, timestamps, results, and failures so the REPL remains responsive.
Acceptance Criteria:

• Long-running service calls do not block prompt redraw, keyboard handling, or live output.
• Users can inspect running, completed, failed, and cancelled jobs.
• Mutating operations are serialized per target resource to prevent concurrent writes to the same GEDCOM, manifest, configuration, or database artifact.

[sodejm]

Current implementation status

Completed and merged in PR #95. The REPL now submits long operations to a bounded worker pool, exposes stable job IDs and serializable lifecycle snapshots, captures sanitized results/failures, and serializes mutations by target resource. jobs list and jobs show JOB_ID provide inspection without blocking the prompt.

Verification completed locally (make test: 401 passed, 8 skipped; lint/type/security green) and all hosted test/security/CodeQL checks passed. Issue closure was verified after merge.