feat: Upgrade Global Presence to SSE architecture

- matrix-presence-aggregator v2 with SSE endpoint
- Created @presence_daemon Matrix user
- SSE proxy in Next.js /api/presence/stream
- Updated frontend to use SSE instead of WebSocket
- Real-time city online count and room presence

services/matrix-presence-aggregator/app/__init__.py

@@ -0,0 +1,2 @@
+# Matrix Presence Aggregator
+