Slack Integration, Feature Flags, and UI Overhaul

Features

• Added full Slack integration with Socket Mode, threaded replies, and UX polish.
• Introduced a unified feature flag system with an experimental agentic-apps flag.
• OpenAI and Anthropic compatibility APIs now pass images through end-to-end.
• CLI workers can now send live-MCP tool call requests to the server over WebSocket.
• System health activity feed now groups agentic thread jobs and suppresses noisy thread tool calls.

Improvements

• Redesigned app shell nav rail layout, icons, and escalation bell animation.
• Comprehensive mobile optimisation pass with reusable components and rem-based sizing tokens.
• Settings page: organisation/team invites (PATCH, copy-link), user soft-delete.
• Dashboard empty states and list page copy improvements.

Fixes

• Resolved Discord message routing, silent drops, and false-positive NO_REPLY classifications.
• Fixed OpenAI/Anthropic many-to-many routing for endpoints with tool call support.