Complete Android download queue management and offline polish

[altaywtf]

Parent

#52

What this delivers

The lean mobile-v1 download path from #28 gains the queue-management and lifecycle polish intentionally deferred from launch: bounded concurrency, understandable queued/running/failed state, bulk cleanup, and completion behavior users can trust.

Scope

• Configurable or product-decided concurrent-download limit with a visible queue.
• Queued, running, paused/retryable, failed, complete, and removed states with deterministic recovery.
• Numeric progress where the platform source provides a trustworthy denominator.
• Multi-select removal of local copies without deleting remote originals unless a separate confirmed action is chosen.
• Completion/failure notifications that deep-link to the local item and respect notification permission state.
• Storage-pressure and unavailable-local-file recovery.

Acceptance criteria

• Queue ordering and concurrency survive process recreation.
• Failed or interrupted downloads recover without silently losing queue state.
• Bulk local deletion cannot delete remote originals implicitly.
• Notification and permission-disabled states are both verified.
• Offline playback and local-availability indicators remain correct after queue operations.

Verification

• State-machine tests with controlled download progress and process restoration.
• Emulator/device recording covering queueing, retry, completion, bulk cleanup, airplane mode, and storage failure.
• ./gradlew verify and mobile debug assemble green.

Blocked by

• Mobile downloads v1: download-to-device with explicit local availability and offline playback #28

Boundaries

• Post-v1; does not gate Epic: native Android rewrite — Compose mobile + Android TV from one codebase #14.
• No public-link or remote-trash behavior.
• Do not persist token-bearing download URLs in logs, notifications, or durable queue metadata.