fix(database): persist import queue skip flags

[javi11]

Manual imports now retain skip_arr_notification and skip_post_import_links in the queue. Both single-item repository paths also apply the latest flags when an eligible row is requeued, while their existing status guards continue to protect active rows.

Closes #964.

Validation:

• Added insert/upsert tests for all flag combinations, including resetting flags and protecting existing row statuses.
• Added an HTTP handler-to-SQLite integration test for true, false, and omitted skip_arr_notification.
• go test ./..., affected package race tests, go vet, and scoped golangci-lint passed.

PostgreSQL variants are included but were skipped locally because ALTMOUNT_TEST_PG_DSN is unset.