Sync web orchestration with rustnzb monorepo

[thedancingdeveloper]

Summary

• sync queue lifecycle, global pause ownership, failure/history persistence, and post-processing behavior from the rustnzb monorepo
• sync direct-unpack compatibility, SABnzbd status mapping, RSS migration, authentication, and log-buffer behavior
• remove dispatcher concerns now owned by nzb-dispatch
• align with nzb-nntp 0.2.23, nzb-decode 0.1.3, nzb-postproc 0.2.7, and nzb-dispatch 0.2.7
• bump nzb-web to 0.4.21

Validation

• cargo fmt --all -- --check
• cargo check --all-features
• cargo test --all-features (72 tests)
• cargo clippy --all-targets --all-features -- -D warnings
• cargo package --allow-dirty