manager: avoid enqueuing paused downloads again

[fhgffy]

download() queries RUNNING, PAUSED and PENDING downloads, but its matching-row check only returns early for RUNNING/PENDING. A paused download therefore falls through to enqueue() when the user requests the same URL or filename again.

Include PAUSED in the existing onDownloading()/early-return branch. Android defines this status as waiting to retry or resume, so the existing job is still active: https://developer.android.com/reference/android/app/DownloadManager#STATUS_PAUSED

Reproduction and checks:

• Compiled the entire production Downloader.kt and LatestVersionInfo.kt with Kotlin 2.4.10 and Java 21 in an external host-JVM harness
• A matching paused row produces an extra enqueue on the base; the patch produces no enqueue and calls onDownloading() once
• The focused suite goes from 10/15 to 15/15 passing, covering URL/title matches, all three active statuses, unrelated rows, null/empty history, request fields, callback exceptions and cursor closure
• A separate review repeated the suite with newly enqueued jobs exposed as PENDING. The base creates one extra request before later calls find it; the patch creates none. Real repeated-request counts depend on provider state and timing
• git diff --check passes

Android/Compose boundaries are test doubles. This external harness is not a committed Android test target and does not test the actual DownloadProvider, network resumption or concurrency. Full Gradle/Android build, lint, emulator/device and UI interruption checks have not been run. Existing URL-or-title matching and completed-download behavior are unchanged.