[WIP] GXS: Improve GXS DB access

[jolavillette]

This PR was entirely created by Gemini

At the moment this PR is for testing purpose only

• Performance: Implemented updateMessageMetaData batching with single SQL transaction and in-memory cache updates, making mass updates instant.
• Stability: Added SQLITE_BUSY retry loop in RetroDb read operations to prevent failures during concurrent writes.
• UI Fix: Grouped mass update notifications in RsGenExchange to prevent event loop starvation and UI freezes.

Code by Gemini

[jolavillette]

Need more work, the performance issue when loading big Channels/Forums/Board is more complicated than DB access