Improve settings workspace UX and reduce routine log noise

[LIU9293]

Summary

• Move Slack workspace removal out of the sidebar and show Remove Workspace beside Save on the Slack workspace settings page.
• Change Add Workspace to open a modal for App Token/Bot Token entry instead of inline sidebar inputs.
• Reduce routine lifecycle logs to debug, consolidate startup readiness log into one line, and bump version to 0.0.50.