v4.8.4; Soulseek reliability fixes for Windows & macOS

Fixes

• Soulseek login test always failed on Windows/macOS (#10): it waited for search results on an inbound listen port, which the default firewall on both platforms blocks; Soulseek authentication itself is outbound-only, which is why Nicotine+ worked fine with the same credentials. The test now checks for the outbound Logged in <user> line from sldl -v instead, so it no longer depends on inbound connectivity.
• Downloads failed whenever Soulseek was the only enabled source and Tidal was down (#8): metadata (artist, title, ISRC) was resolved exclusively through the Tidal proxy, so the Fetch button stayed disabled with no Tidal reachable, and Soulseek was never actually reached. The Universal (Deezer) search tab now provides a fully Tidal-independent path: it resolves metadata from the public Deezer API and routes straight to the orchestrator, which can search Soulseek by title and artist alone, no ISRC required.

Internal

• sldl's search timeout raised to 12s to tolerate slower indirect (server-mediated) peer connections on firewalled clients, plus a startup log when Soulseek is enabled but fails to initialize.
• Core dependency bumped to v0.10.4.

Full Changelog: v4.8.3...v4.8.4