Fix Qortal gateway group discovery

[QuickMythril]

Summary

• seed the accountless Qortal gateway sidebar from the bounded public /chat/groupstats feed, resolve only open groups, and retain a selected public group across refresh expiry
• make explicit Qortal group search use a complete session-cached catalogue, ranked by name or numeric group ID, independent of current chat activity
• show closed/private catalogue matches through the existing lock and unavailable UX without attempting private reads
• bump Chat to 2.0.5 and extend unit plus real gateway browser coverage

Bounds

• gateway discovery is capped at 50 candidates with four concurrent metadata/message workers
• refresh runs every 60 seconds only while the tab is visible
• no account or write actions are used in gateway mode

Verification

• npm test — 52 files, 719 tests passed
• npm run build
• npm run smoke:new-user
• npm run smoke:gateway
• npm run smoke:hub-private
• git diff --check