Fix empty/hanging WinGet Discover after the Turso migration

[Gabriel Dufresne (GabrielDuf)]

Since the Turso SQLite migration shipped in 0.8.0, UniGetUI's page returns no results from the winget source ("Failed when searching source: winget"), and pinget source update intermittently fails with Access is denied (os error 5). This PR fixes both and bumps the version to 0.8.1.

Fix

• emit a non-correlated rowid IN (SELECT owner FROM map JOIN value …) so the owner-id set is evaluated once (LIST SUBQUERY + bloom filter) instead of per row. Applied identically to the Rust core and C# core.
• if the overwrite is blocked, pinget now: waits and retries a few times — most locks (like an AV scan) are gone within milliseconds; then if it's still blocked, renames the old index out of the way and moves the new one in. This works even while another pinget is still reading the old file, because SQLite keeps the open file alive until that reader finishes. The renamed-aside copy is only deleted once the new index is safely in place, and put back if anything goes wrong — so a working index is never lost.