feat: integrate mixed-source regular playlists

[jm2]

Summary

• Integrate authenticated Subsonic, Jellyfin, Plex, and DAAP tracks into regular Tributary playlists using exact source-scoped identity.
• Preserve playlist order and duplicate occurrences, render localized unavailable rows when a source or track disappears, and remove the exact selected occurrence.
• Route remote playback and artwork through current-session source authority while keeping ratings and playback history local-only.
• Make multi-track additions all-or-none: stage the SQL transaction, acquire exact current source authority immediately before commit, roll back if refresh or disconnect wins, and retain commit permits until commit or rollback completes.
• Refuse mixed-source or unresolved regular-playlist XSPF export before touching the destination instead of silently truncating it to local tracks.
• Update the README, changelog, task tracker, roadmap, source-scoped playlist contract, lifecycle architecture, and all 13 locales.

Review follow-up

• Fixed Rust 1.97 Clippy manual_option_zip compatibility.
• Closed the reported authority time-of-check/time-of-use race by coupling final validation and authority ownership to the database transaction.
• Added deterministic coverage for disconnect-wins rollback, catalogue replacement, permit revocation, current-thread commit versus disconnect, cancellation-safe completion ownership, duplicate guard deduplication, and all-or-none XSPF refusal.

Validation

• cargo test --release: 1,144 passed
• cargo +1.92 check --all-targets --locked
• cargo clippy --all-targets --all-features -- -D warnings
• cargo clippy --release -- -D warnings
• cargo build --release --all-features
• cargo fmt --all -- --check
• git diff --check

Implements the mixed-source regular-playlist portion of #47. Import and pull synchronization of playlists owned by a Subsonic server remain a separate follow-up capability.

[gemini-code-assist]

Code Review

This pull request implements end-to-end support for mixed-source regular playlists (PR #142), allowing users to combine local tracks with entries from authenticated Subsonic, Jellyfin, Plex, and DAAP catalogues. Key changes include atomic all-or-none additions, exact removal of duplicate or unavailable entries using durable occurrence IDs, and a robust projection layer that renders explicit localized unavailable rows for disconnected sources or missing tracks. Additionally, the playback queue now tracks per-row media ownership and revalidates transient closed guards at the point of use for remote stream and artwork resolution. Rating writes and playback history remain restricted to local tracks. There are no review comments provided, so I have no feedback to evaluate.

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[chatgpt-codex-connector]

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